Pathology of malignant melanoma

Surg Clin N Am 83 (2003) 31–60

Pathology of malignant melanoma Vincent Liu, MD*, Martin C. Mihm, MD Massachusetts General Hospital, Dermatopathology Unit, Warren 829, 55 Fruit Street, Boston, MA 02114, USA

Understanding the fundamental aspects of the pathology of melanoma is crucial for the surgeon to deliver optimal care to the patient with melanoma. Pathology provides diagnostic data, offers prognostic information, and, to a large extent, directs management. This article reviews several aspects of the pathology of melanoma, with special relevance to the surgeon, including benign clinicopathologic simulators of melanoma, fundamental concepts of the pathology of melanoma, histopathologic prognostic factors of melanoma, approach to lymph nodes, and implications of the revised staging system.

Benign clinicopathologic simulators of melanoma Some pigmented lesions can mimic melanoma clinically or histologically. Additionally, some of these lesions, although without metastatic capacity themselves, are believed to possess premalignant potential, and thereby serve as potential precursors to melanoma. Several of these benign simulants of melanoma will be discussed in this section. Others, including cellular blue nevi, deep penetrating nevi, and cutaneous neurocristic hamartomas, are beyond the scope of this article but are dealt with in detail in other sources [1]. Dysplastic nevus Dysplastic nevi are believed to occupy an intermediate zone between benign nevi and melanoma [2]. Admittedly, the source of some controversy [3], dysplastic nevi are significant for being potential precursors to melanoma and as being independent risk factors for melanoma [4,5]. In

* Corresponding author. E-mail address: [email protected] (V. Liu). 0039-6109/03/$ - see front matter Ó 2003, Elsevier Science (USA). All rights reserved. doi:10.1016/S0039-6109(03)00003-3

32

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

the context of the dysplastic nevus syndrome they are considered a marker for heritable melanoma [6]. Therefore, their recognition and distinction from melanoma is important for the clinician and pathologist. Clinically, dysplastic nevi appear as flat macules or thin ‘‘pebbly’’ plaques that display Asymmetry, Border irregularity, Color variation, and usually a Diameter that is greater than 5 mm. These ‘‘ABCD’’ diagnostic criteria of melanoma, when applied to dysplastic nevi, are generally less evolved. Dysplastic nevi are located preferentially on the trunk, although the extremities, particularly in women, are also common sites. Histologically, dysplastic nevi are defined by two major and four minor architectural and cytologic criteria (Fig. 1) [7]. The first essential major feature is the proliferation of variably atypical basilar melanocytes that characteristically extend three rete ridges beyond the dermal nevic component, a phenomenon called ‘‘shouldering’’. The degree of melanocytic atypia may be graded on a spectrum of slight-moderate-severe, with progression according to increasing cellular and nuclear size, and nuclear chromatism. Midlevel spinous keratinocytes offer a ready benchmark for size comparison. Arrangement of these atypical melanocytes in either a lentiginous or an epithelioid pattern comprises the second major criterion for diagnosis of dysplastic nevi. The lentiginous pattern describes a hyperplastic epidermis with elongate rete ridges, along which are discontinuously arrayed, atypical nevomelanocytic cells. The second pattern for the dysplastic nevus is one of epithelioid dysplasia which displays prominent, round cells with pigmentstippled, ample cytoplasm, and large, round, nucleolated nucleoli with a relatively low nuclear:cytoplasmic ratio. These cells are situated discontinuously along the basal layer of a generally normal epidermis.

Fig. 1. Dysplastic nevus. A compound melanocytic nevus demonstrating shouldering (extension of junctional nests three rete ridges beyond the dermal components), bridging of adjacent nests, lamellar and concentric fibrosis, and an inflammatory infiltrate. Cytologic atypia as manifested by large, chromatic nuclei is also evident.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

33

In either pattern, four host stromal responses were identified to be supportive histologic criteria in diagnosing dysplastic nevi. Dermal fibrosis is one supportive histologic feature, and occurs beneath the dermal rete as lamellations (lamellar fibrosis), or as condensations that hug the rete tips (concentric fibrosis). A second supportive feature is cohesion or ‘‘bridging’’ between adjacent junctional nevomelanocytic nests. A perivascular or lichenoid (‘‘bandlike’’) inflammatory infiltrate within the papillary dermis, and increased vascularity are further features that are applied as minor criteria. The presence of the two major and two of the four minor criteria is sufficient for diagnosis of a dysplastic nevus (Fig. 1) [8]. Atypical melanocytic hyperplasia Atypical melanocytic hyperplasia, in our usage, refers to a presumed early phase of development of either superficial spreading melanoma, acral lentiginous melanoma, or even lentigo maligna. Clinically, these lesions manifest as flat, tan to brown, irregularly shaped and irregularly bordered macules. Although not a wholly banal lentiginous proliferation, atypical melanocytic hyperplasia may be viewed as existing toward the benign end of the melanocytic lesion spectrum, though with premalignant potential. Atypical melanocytic hyperplasia more specifically describes a proliferation of atypical melanocytes that are disposed predominantly along the basal epidermal layer. In the precursor to superficial spreading melanoma, the melanocytic pattern demonstrates epithelioid and spindled cells that are arranged in lentiginous array. The acral lentiginous variant displays dendritic cells that are scattered irregularly along the dermal–epidermal junction. Scattered, randomly situated, discontiguous, pleomorphic intrabasilar melanocytes characterize early lentigo maligna. Distinction from melanoma in situ is made by the lesser degree of cytologic atypia, the lack of confluence of atypical melanocytes, and the lack of pagetoid spread. Spitz nevus Named after its original descriptor, Sophie Spitz, the compound nevus of Spitz is one of the most challenging clinical and histologic mimics to melanoma [9]. The early reference to the lesion as ‘‘benign childhood melanoma’’ attests to its superficial resemblance to a malignant entity. Clinically, the lesions present as rapidly growing, dome-shaped, pink-tan papules, 0.5 to 1.0 cm in diameter, occurring classically in children, and less commonly, in adults [10,11]. Spitz nevi favor the head or neck; the dorsa or the hands and arms, thighs, buttocks, and trunk are other sites of predilection. One helpful clue to diagnosis is elicited by pressing the lesion with a glass slide (a technique called diascopy). The persistence of a rim of darker brown pigmentation often occurs in Spitz nevi with compression of the lesion’s dilated, ectatic vascular spaces.

34

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Composed of a proliferation of spindled and epithelioid nevomelanocytes in a variably hyperplastic epidermis, the classic Spitz nevus histologically demonstrates a characteristic ‘‘inverted triangle’’ architectural pattern, whose long axis lies along the dermo–epidermal junction and whose apex points toward the deep dermis. Parallel orientation of the long axes of the spindle cells in their nests has been likened to a ‘‘raining down’’ pattern of a school of fish. Nevomelanocytes with giant nuclei in single or multinucleate forms may be admixed with the typical Spitz nevomelanocyte, usually within the superficial portion of the lesion; epithelioid-type nevomelanocytes are usually present in varying numbers. Melanin pigmentation is often observed in or fine or coarse granules in paranuclear location. Eosinophilic globules (Kamino bodies) are further diagnostic clues [12]. Histologically, these lesions can appear quite worrisome at first-glance (Fig. 2). The spindled and epithelioid cells can be rather large and pleomorphic, with delicate nuclear membranes, large, often blue nucleoli, and wispy cytoplasm, contain mitotic figures superficially, and even show upward (pagetoid) spread of cells and small nests into the higher layers of the epidermis [13]. The nevus is required to demonstrate maturation, however, defined by diminution in size from superficial to deep dermis; atypical or deep mitoses are not allowed. Variable other features of the Spitz nevus are papillary dermal edema and vessel ectasia. Recognition of a set of lesions composed of cells with generally Spitzoid morphology, but which deviate from the prototypical pattern of a compound Spitz nevus by virtue of variant architectural pattern or cytologic atypia, has led to their labeling as ‘‘atypical Spitz’’ tumors [14]. Such cases represent an extremely difficult area in dermatopathology; such lesions typically exhibit borderline features that overlap with Spitzoid melanoma [15]. In such

Fig. 2. Spitz (spindled and epithelioid cell) nevus. A compound melanocytic nevus exhibiting symmetry, and cells of epithelioid (abundant eosinophilic cytoplasm, large, round nuclei) and spindle cell morphology. Maturation is reflected by the similarity of cells at any given horizontal level of the lesion.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

35

instances, prediction of biologic behavior with certainty is not possible, and therapy needs to be adjusted accordingly. Spindle cell nevus of Reed The pigmented spindle cell nevus of Reed is viewed by many investigators as a variant of the Spitz nevus [16]. Its morphology is typified by a uniformly dark brown-black papule with a peripheral ‘‘flare’’. This lesion clinically favors the dorsal thighs of women in the third and fourth decades of life, although men and other age groups are susceptible as well. Histology demonstrates a well-demarcated, symmetrical melanocytic nested lesion that occupies the dermo–epidermal junction, with occasional extension into the superficial dermis. The pigmented spindle cells are arranged in nests which resemble bunches of bananas to some degree and can expand the rete in which they lie (Fig. 3). Cytologically, the cells resemble those of the Spitz nevus, with particularly striking coarse granular melanin pigmentation. The practical relevance of recognition of such a lesion lies in its distinction from melanoma; its dark pigmentation can confer superficial resemblance to a malignant tumor, although the lesion is benign [17]. ‘‘Genital-type’’ nevus Another pigmented lesion that can create confusion by its resemblance to melanoma, clinically and histologically, is found in flexural areas and particularly along the ‘‘milkline’’, extending into the genito-iguinal regions. This lesion has not yet been well-characterized with regard to strict histologic criteria, and its true prognosis is still being elucidated [18]. In general, however, these lesions possess prominent, often large, oval junctional nests, and exhibit some cellular atypia. Particular stromal responses have been described as well [19].

Fig. 3. Pigmented spindle cell nevus of Reed. Well-demarcated, symmetrical, junctional melanocytic nevus composed of large junctional nests made up of prominently pigmented spindled cells.

36

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Melanoma: phases and evolution The ability to distinguish melanomas with metastatic potential from melanomas with indolent behavior would be an invaluable prognostic tool. An attempt to model such a distinction has been reflected in the concepts of ‘‘radial’’ (nontumorigenic) and ‘‘vertical’’ (tumorigenic) growth phase, which are posited as stages in step-wise tumor progression [20]. Radial growth phase Radial growth phase (RGP) describes the early stage of melanoma, in which the tumor is thin, and primarily intraepidermal in location. Two possible settings exist for RGP, in situ melanomas (restricted to the epidermis) and microinvasive melanomas (microscopic papillary dermal extension present). Malignant melanoma in situ In situ melanoma refers to the proliferation of malignant melanocytes that are restricted to the epidermis. By definition, malignant melanoma in situ (MMIS) is a form of radial growth phase melanoma. Three forms of in situ melanoma may be identified. Characteristic of the superficial spreading variant of MMIS is extensive pagetoid spread, with malignant melanocytes extending throughout the epidermis, even into the corneal layer. The histologic picture of acral lentiginous melanoma in situ is that of uniformly atypical dendritic melanocytes aligned in contiguous array along the dermo– epidermal junction. Some difference of opinion surrounds the third variant of in situ melanoma, known as lentigo maligna (LM). Some investigators restrict the term LM to refer to a purely premalignant state, a precursor to melanoma in situ-lentigo maligna type [21]. In contrast to MMIS-lentigo maligna type, in LM the lentiginous proliferation is purportedly less contiguous, the cell density is not as high, and pagetoid spread is not full thickness. Obviously, the distinction is a matter of degree; LM and MMISlentigo maligna type can be viewed as neighbors on a spectrum of malignancy. After invasion occurs, the lesion has become lentigo maligna melanoma (LMM). Microinvasive RGP melanoma By one strict definition, radial growth phase melanomas comprise either in situ melanomas or particular thin lesions limited to those in which the largest dermal nest is no larger than the largest epidermal nest, and in which there are no dermal mitoses [22]. In such compound RGP melanomas, the morphology of the dermal nevomelanocytes is similar to the epidermal component (Fig. 4). An inflammatory infiltrate is characteristically associated with the radial growth phase, which is composed predominantly of lymphocytes with admixed macrophages and melanophages.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

37

Fig. 4. Radial growth phase melanoma. Pleomorphic melanocytes with large, hyperchromatic nuclei are arranged singly and in nests in the epidermis with confluence. Dermal microinvasion is present, but involvement is limited to the papillary dermis, there are no dermal nests larger than the largest epidermal nest, and there are no dermal mitoses.

Vertical growth phase Vertical growth phase (VGP) is the stage of melanoma with clear metastatic potential. This tumorigenic stage of melanoma may arise in the background of radial growth phase melanoma, or it may occur de novo. By definition, these lesions histologically possess either at least one dermal mitosis or a dermal nest larger than the largest epidermal nest. Melanoma subtypes In RGP and VGP melanoma, variable cell types and distribution allow subclassification of melanoma histology [23]. These histologic subtypes of melanoma are important, primarily for their recognition as they do not directly correlate with behavior.

Superficial spreading melanoma Superficial spreading melanoma (SSM) is the most common form of melanoma. Clinically, a variably pigmented plaque with irregular and often notched, borders is seen, ranging from a few millimeters to several centimeters. Shades of tan-brown to jet-black, and from red to blue, are seen in these lesions. Progressive centrifugal proliferation of atypical melanocytes manifests clinically as an asymmetric peripheral flare. SSM may occur at any anatomic site at any age, although there is a predilection for the back in men, and the legs in women. Histology of SSM is characterized by asymmetry, poor circumscription, and lack of maturation (Fig. 5) [24]. Single cell pagetoid spread of atypical

38

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Fig. 5. Superficial spreading melanoma. Compound melanocytic nested proliferation composed of epidermal nests of varying shapes and sizes disposed irregularly along the dermo–epidermal junction often with associated prominent pagetoid spread, overlying a dermal component showing cytologic atypia and mitoses.

melanocytes throughout the layers of the epidermis confers an appearance that resembles buckshot scatter. Cytologically, the melanocytes are often, although not always, epithelioid in morphology, with large brown nuclei, prominent eosinophilic nucleoli, and ample cytoplasm filled with fine melanin granules. Dyshesion of nests is also a common component of SSM. In RGP SSM, infiltrates of single cells or small nests can occur into the papillary dermis, which is sometimes slightly widened by fibrosis and an associated inflammatory lymphocytic infiltrate. In cases of VGP SSM the epidermal component extends beyond three rete ridges of the dermal component, a criterion that is useful in distinguishing this lesion from nodular MM.

Lentigo maligna melanoma Lentigo maligna melanoma arises on chronically sun-exposed sites in older individuals and presents as a freckle-like lesion [25]. The lesion begins as an irregular flat, variably pigmented, tan-brown patch which gradually grows and develops darker, asymmetric flecks in areas. Partial regression is not uncommon. In approximately 5%, palpable induration or nodules develop, which signal invasion and transformation to lentigo maligna melanoma [26]. Histologically the lesion manifests epidermal atrophy, solar elastosis, and atypical melanocytes that are arrayed along the dermo–epidermal junction in lentiginous pattern (Fig. 6). The melanocytes are pleomorphic and display irregular shapes and forms with variably hyperchromatic nuclei. Many of the tumor cells display a shrunken cytoplasm around pale nuclei with small pink nucleoli. The melanocytes usually are lined up contiguously, and nests

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

39

Fig. 6. Lentigo maligna melanoma. Contiguous lentiginous single cell and nested proliferation of atypical melanocytes with pagetoid spread and extension down follicular epithelium.

may be confluent. Characteristically, the lentiginous proliferation extends down the external root sheath of hair follicles, a feature that accounts for a high recurrence rate for superficially ablated lesions. Mitoses may be detected, and pagetoid spread is common, particularly in areas of invasive LMM. Melanophages and inflammation are also typical accompanying features in LM and LMM. Acral lentiginous melanoma Acral lentiginous melanoma arises on palmar, plantar, subungual, and occasionally, mucosal surfaces as dark brown to black, irregular, unevenly pigmented patches [27]. There is a predilection for the soles. This melanoma subtype represents the least common variant of the RGP forms overall; however, it is the most common presenting form in Asians. Nodularity and ulceration signal invasion. The histologic appellation refers to the characteristic single-cell proliferation along the dermo–epidermal junction. Histology demonstrates hyperkeratosis, irregular, often large, junctional nests with atypical melanocytes that may exhibit pagetoid spread. The atypical melanocytes are characterized by large, nucleolated, nuclei, with large nuclear:cytoplasmic ratios. Dendritic processes are often highlighted by melanin granules. Confluence of these dermo-epidermal nests can also be associated with microinvasion of single cells into the papillary dermis in the radial growth phase. An underlying lymphocytic infiltrate with admixed melanophages is common (Fig. 7). Nodular melanoma Nodular melanoma by definition is vertical growth phase melanoma [28]. Presentation as a darkly pigmented nodule or tumor is typical, although

40

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Fig. 7. Acral lentiginous melanoma. Large atypical melanocytes with dendritic morphology disposed in single cell and nested lentiginous array with foci of pagetoid growth.

amelanotic versions occur as well. The nodules may be polypoid or pedunculated [29]. Although the lesion is primarily dermal, the large expansile component may be associated with an epidermal component as well; however, by definition, the epidermal component does not extend beyond three rete ridges of the dermal component (Fig. 8). Mitoses are present and may be atypical. Cytologically, the component cells may be epithelioid or spindled. Rare variants of vertical growth phase melanoma

Minimal deviation melanoma Minimal deviation melanoma refers to vertical growth phase melanoma that demonstrates little cytologic variation [30]. The term was coined to

Fig. 8. Nodular melanoma. (A) Large cellular nodule of atypical and mitotically active melanocytes lacking maturation (B).

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

41

describe a melanocytic neoplasm with intermediate prognosis. As such, the traditional histologic prognostic factors of fully evolved melanoma, including measured depth, level of invasion, ulceration, and host response, are not conventionally reported for minimal deviation melanoma. Suffering from limited case numbers, lack of long-term reported follow-up, and use of imprecise, variable diagnostic criteria, this entity has generated confusion and controversy. Given its historical importance, and recognition that such an intermediate category of melanocytic neoplasms exists, however, a brief discussion is warranted. Histologically, this lesion exists as a tumor nodule, usually expanding the papillary dermis. The constituent cells consist of cells whose morphology is that of the epithelioid and spindle cell nevus type, with some tumors exhibiting typical type ‘‘A’’, type ‘‘B’’, and type ‘‘C’’ nevomelanocytes of normally developing nevi. Infiltration of single cells into the reticular dermis may be observed in some cases, and usually involving spindle cells. The uniformity of the population of cells contrasts with the expected pleomorphism of more conventional melanoma. Minimal deviation melanoma lacks the ‘‘maturation’’ of wholly benign melanocyte lesions, however. Mitoses may be present, but are only a few in number. Sometimes there is a radial growth phase, in contrast with fully evolved melanoma, the cells in the radial growth phase are identical to those in the vertical growth phase (Fig. 9). Minimal deviation melanoma may arise de novo, but it may also arise in the context of pre-existing tumors, such as Spitz nevi, pigmented spindle cell nevi, congenital nevi, or acquired nevi. In such cases, the expansile nodule of the minimal deviation melanoma lies adjacent to areas of recognizable precursor lesion. Minimal deviation melanoma may also elicit a desmoplastic response. The plump epithelioid and spindle cell morphology of these tumor cells contrasts with the hyperchromasia and pleomorphism of desmoplastic melanoma.

Fig. 9. Minimal deviation melanoma. (A) Dermal nodule composed of a uniform population of (B) moderately atypical, primarily Type A, nevomelanocytes arranged in fascicles intercalated in the background collagenous stroma, with no tumor necrosis and minimal host response.

42

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Nevoid melanoma So-named for its superficial clinical and histologic resemblance to a melanocytic nevus, nevoid melanoma presents as either a verrucous or a dome-shaped nodule [31]. Unlike a benign melanocytic nevus, however, the behavior of such a lesion is that of melanoma, with full metastatic potential [32]. Clinically, these lesions usually occur on the trunk or proximal limbs of young adults [33]. Nevoid melanoma, like minimal deviation melanoma, has a large dermal component, but in contrast to minimal deviation melanoma, the dermal component represents frank vertical growth phase in nevoid melanoma. Cytologically, two variants of nevoid melanoma are recognized; one contains large cells that resemble Spitz nevi and the other contains nevuslike small cells. In both types, there is striking cellularity with hyperchromasia. Moreover, unlike banal nevi, although there seems to be diminution of cell and nest size with depth of the lesion, there is no true maturation in nevoid melanoma. This ‘‘pseudomaturation’’ is revealed by malignant cytology of cells in the deepest reaches of the tumor, with readily observed mitoses (Fig. 10). Immunohistochemical staining with proliferation antigens and HMB-45 may be of diagnostic value [34].

Infantile and childhood melanoma Fortunately, melanoma in those under age twenty is a rare phenomenon, and makes up less than 5% of all melanomas [35]. Melanomas in children and adolescents may be viewed as occurring in three settings: (1) congenitally, either from transplacental transfer or in the context of large congenital nevi; (2) arising de novo; and (3) arising in the background of pre-existing melanocytic lesions, most commonly, either dysplastic nevi or congenital nevi.

Fig. 10. Nevoid melanoma. (A) A generally symmetrical melanocytic dermal nodule demonstrating ‘‘pseudomaturation’’: decrease in cell and nest size with depth, but (B) pleomorphism, nuclear atypia, and mitoses in the depths of the tumor.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

43

Histologically, three patterns of congenital or pre-existing nevus-associated melanoma can be recognized: (1) most commonly, as a variant of the common types of melanoma seen in adults; (2) occasionally, as a nodule of primitive malignant melanocytes; and (3) in the context of malignant Spitz nevus. In the second setting, a well-defined dermal nodule is identified that is sharply demarcated from the adjacent nevus cells. Its cells are hyperchromatic and exhibit mitoses, often with atypical forms. Zonal necrosis may be present. A lymphocytic infiltrate is commonly found. With regard to Spitz tumors, worrisome features that suggest malignant transformation have been identified specifically. The presence of ulceration, large size (>1 cm), asymmetry, hypercellularity, lack of maturation, prominent cytologic atypia, prominent mitoses, deep mitoses, and atypical mitoses [16,36] are ominous signs. Desmoplastic melanoma Desmoplastic melanoma appears as an ill-defined plaque or nodule that often lacks pigmentation and is a particularly challenging form of melanoma to recognize clinically, identify histologically, and manage effectively [37]. Favoring sun-exposed areas on the head and neck, desmoplastic melanoma characteristically arises in the context of an associated lentigo maligna. Desmoplastic melanoma is composed of spindle-shaped, malignant melanocytes that resemble fibroblasts seen in scars and histologically is often seen with overlying lentiginous melanocytic hyperplasia, sometimes lentigo maligna (Fig. 11) [38]. Fascicles of hyperchromatic spindle cells may be observed at acute angulation to the epidermis. There is a striking increase in spindle cells with hyperchromatic, irregularly-shaped elongate nuclei admixed with a fibrous response. These cells can form neuroidal structures. Neurotropism is often noted. Aggregates of lymphocytes are present and often focal dermal mucin deposits may be found. Given the often subtle resemblance to spindle shaped fibroblasts, the tumor cells of desmoplastic melanoma are vulnerable to inadequate surgical resection which explains its increased recurrence rate. Immunohistochemical staining with S-100 protein can aid in diagnosis and delineation of margins. Pigment-synthesizing melanoma A variant of melanoma that was recently recognized in humans is one that bears resemblance to that originally described in horses, the so-called equine-type or pigment-synthesizing melanoma (Fig. 12) [39]. Given the small numbers that have been reported thus far, no clear sex or site predilection has been discerned with certainty. Composed of intensely pigmented, fascicular spindle cells, this tumor typically extends to subcutaneous fat [40]. Notably, pigment-synthesizing melanoma has a propensity

44

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Fig. 11. Desmoplastic melanoma. (A) Proliferation of spindle-shaped cells with nuclear hyperchromasia and atypia in the dermis (B), with overlying lentigo maligna. (C) The melanocytic nature of the dermal spindle cells is demonstrated by S-100 positivity.

to lymph node metastasis; however, these patients seem to have a good prognosis although further studies need to be done.

Metastatic melanoma With an increased thickness of a primary tumor comes an increased risk for metastasis. For melanoma, lymph nodes represent the primary metastatic sites; skin, subcutaneous soft tissue, lung, and brain are common secondary targets. In the skin, metastases present as nodules or plaque-likes lesions, classically in proximity to the primary tumor. Characteristic of the histology of melanoma metastases is the presence of variably sized dermal nodules without epidermal connection, and often without significant lymphocytic response [41]. Epidermal involvement can rarely occur in epidermtropic metastases [42].

Prognostic factors Beyond confirming a diagnosis, the role of pathology is to offer clues to biologic behavior. Multivariate analysis has been performed on several

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

45

Fig. 12. Pigment-synthesizing melanoma. (A) A heavily pigmented, spindle-cell tumor (B) dissecting through the dermis in fascicles.

histologic variables to determine which parameters might be significant in predicting prognosis for melanoma [43]. Among the histopathologic factors that were shown to be predictive of course include linear depth, histologic level, mitotic rate, inflammatory (lymphocytic) response, and ulceration. Similarly, the clinical characteristics that were found in some studies to possess prognostic significance include tumor site (extremities more favorable) [44], sex (female more favorable) [45], and age (younger more favorable) [46].

Tumor thickness (Breslow thickness) Vertical depth of tumor invasion, recognized more than 30 years ago to reflect likelihood of metastasis, has become the single most important prognostic aspect of a primary melanoma [47,48]. For this variable to be useful, however, it must be measured accurately. As standardly defined, thickness is measured from the top of the granular layer down to the deepest reaches of the dermal component. In cases of ulcerated lesions, the top boundary should be measured from the base of the ulcer. Areas of perifollicular or perieccrine nests which are invested by periadnexal adventitial stroma, are regarded as periadnexal in origin, and thus are not measured as the deepest point of invasion.

46

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Although thickness remains the most powerful predictor of metastatic risk of a primary melanoma, the phenomenon of metastatic ‘‘thin’’ melanomas indicates that other variables act as adjunctive determinants of behavior. Clark’s level of invasion An alternative method to measuring thickness to assess the degree of vertical melanoma invasion is offered by Clark’s microanatomic level [20]. Clark defined these as follows: Level I - melanoma limited to the epidermis; Level II - melanoma extending, but not filling, the papillary dermis; Level III - melanoma filling the papillary dermis; Level IV - melanoma infiltrating into the reticular dermis; Level V - melanoma involving the subcutaneous fat (Fig. 13). It was postulated that penetration of melanoma through the different microanatomic layers of the skin would be directly proportional to an increased chance for metastasis, and thus, a worse prognosis. Intuitively, invasion of malignant tumor down through levels of the skin involves transgressing natural microanatomic borders and affords greater access to lymphovascular and neural conduits for metastasis; therefore, increasingly

Fig. 13. Clark anatomic levels of invasion. Microanatomic invasion into the skin as reflected by Clark levels: (A) Level I - intraepidermal; (B) Level II - papillary dermal involvement; (C) Level III - filling of papillary dermis; (D) Level IV- extension into reticular dermis; V- infiltration into subcutaneous fat (not shown).

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

47

deep involvement should correlate with greater propensity for metastasis. By multivariate analysis, however, Clark anatomic levels were shown to be less statistically significant than Breslow thickness as a prognostic variable [49]. The one subset for which the value of the Clark microanatomic level as an independent prognostic parameter is retained is in so-called ‘‘thin’’ melanomas [50]. Primary melanomas less than 1 mm, which should have a good prognosis according to Breslow thickness, can demonstrate a surprisingly high rate of metastasis if they invade to a comparatively deep anatomic level (III, IV) [51]. Mitoses Mitotic activity was demonstrated by multivariate analysis to be a prognostically significant variable [52]. The threshold of six mitoses per square millimeter has been used to distinguish low from high metastatic risk. The product of mitotic activity and thickness may offer a particularly useful prognostic index [53]. Ulceration Recently, ulceration was added to the list of pathologic variables that have been shown to be a relevant indicator of behavior of melanoma [54]. Specifically, the width of the ulcer was demonstrated correlate with prognosis; ulcers larger than 6 mm are highly associated with nodal metastases [55]. For this finding to be useful, however, it is required that ulceration display active host-response with inflammation as well as fibrin debris. Tumor infiltrating lymphocytes Infiltration of lymphocytes into melanomas was determined to be pertinent to melanoma prognosis [56]. Three patterns of tumor infiltrating lymphocytes are recognized. A ‘‘brisk’’ pattern of lymphocytic infiltration requires lymphocytes to diffusely invest the melanoma nodule, intercalating between, and coming in direct continuity with, tumor cells. Alternatively, a diffuse band under the tumor can also constitute a ‘‘brisk’’ pattern. These ‘‘brisk’’ tumor infiltrating lymphocytic patterns have been associated with a good prognosis, whereas an absent infiltrate, in which either no lymphocytes are present or lymphocytes are present but are not intimately interacting with melanoma cells, portends a poor prognosis. A ‘‘nonbrisk’’ pattern, wherein focal lymphocytes are present, confers an intermediate prognosis. Regression In contrast with tumor infiltrating lymphocytes, the presence of regression in primary melanoma seems to carry negative prognostic

48

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

implications [57]. Defined as focal complete replacement of melanoma by delicate dermal fibrosis, lymphocytic infiltrate, and melanophages, areas of regression require adjacent intraepidermal melanoma to be present. It has been speculated that regression may lead one to underestimate the depth of involvement, thereby resulting in a misleadingly ‘‘thin’’ Breslow measurement. Microscopic satellites Deposits of tumor that are larger than 0.05 mm in diameter and are discontiguous from the main body of Stage IV or V melanoma, are considered ‘‘microscopic satellites’’ when they are identified in the section used for Breslow measurement [58]. Viewed as an intermediate stage between localized tumor and metastasis, microscopic satellites have been reported to be associated with decreased survival [59]. Sentinel lymph node status The sentinel lymph node technique establishes whether there are microscopic deposits of melanoma in the first or sentinel node draining the melanoma. Sentinel node positivity is one of the more powerful predictors of prognosis [60], and will be discussed in the section about lymph nodes. Biologic and molecular variables In the search for new, more powerful, prognostic indicators, attention has turned from microscopic parameters to molecular markers that are related to tumor progression or metastatic evolution [61]. These molecular markers are the latest candidates to be actively evaluated for their prognostic value, diagnostic usefulness, and clues to pathobiology. Conceptually, these candidate markers can be viewed in terms of their particular roles in malignant tranformation. These ancillary prognostic factors include structural DNA alterations, cell proliferation markers, cell adhesion molecules, tumor suppressor genes, growth factors, apoptotic factors, and mediators of invasion, progression, and metastasis. Tumorigenesis may be initiated by alterations in DNA as reflected by aneuploidy, nuclear volume, or altered chromosomal structure. Aneuploidy and increased nuclear volume were reported to be associated with bleaker prognosis [62,63]. Another potentially useful DNA prognostic indicator is represented by nucleolar organizer regions (AgNORs) comprising chromosomal loops of DNA associated with acidic proteins. Detected by silver staining as microscopic nuclear black dots, these AgNORS have been directly correlated with malignancy; in some studies, higher AgNOR counts predicted a worse prognosis [64]. Proliferation markers and cell cycle regulating proteins make up another set of potential prognostically useful indicators. Of particular mention is the

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

49

use of MIB-1 antibody (Ki-67 in frozen tissue) as a reflection of mitotic activity, and thereby, prognosis [65,66]. Similarly, proliferating cell nuclear antigen was variably shown to be correlated with a likelihood of metasasis [67]. Cell cycle regulating proteins that have been examined for possible prognostic usefulness include the products of the p53 [68] and p16 (INK4A/ MTS-1/CDKN2A) genes. The p16 gene product inhibits cyclin-dependent kinase-4, and thereby functions as a tumor suppressor gene [69]. Mutant p16 may lead to progression of the cell cycle and tumor proliferation by phosphorylation of the retinoblastoma gene [70]. Melastatin, another tumor suppressor gene that was recently characterized, holds particular promise as a prognostic indicator. A putative calcium channel regulating protein, melastatin expression in primary melanomas was recently shown to be inversely correlated with metastatic risk [71]. Adhesion molecules constitute another category of molecules that are under scrutiny for possible prognostic benefit in melanoma. Intercellular cellular adhesion molecule-1 (ICAM-1), various integrins, and CD44 cell surface glycoproteins are particularly promising targets for study. A mediator of lymphocyte aggregation and endothelial adhesion, ICAM-1 is upregulated with melanoma progression and may correlate with increased metastatic risk [72]. Similarly, members of the integrin family of molecules, which consist of transmembrane heterodimeric molecules, serve to mediate tumor-extracellular matrix interactions [73]. Integrins were suggested to influence melanoma progression by way of roles in cell adhesion, signal transduction, and angiogenesis. Studies of expression of avb3, a4b1, and a2b1 suggested a correlation with recurrence, metastasis, and mortality [74]. Likewise, b-catenin is crucial in the function of cell adhesion molecules and participates in growth regulatory signalling pathways that may be involved in malignant transformation. Loss of b-catenin expression was reported to be associated with disease progression in malignant melanoma [75]. Growth factors and their receptors, including epidermal growth factor receptor, insulin growth factor 1, and transforming growth factor beta, are possible indicators of melanoma prognosis [76]. In experimental models, expression levels of the transcription factor, nuclear factor-kappaB (NFjB), were correlated with antiapoptosis, angiogenesis, and metastasis [77]. In fact, NF-jB serves as a pharmaceutical target in human myeloma [78]. The experimental drug LDP-341 (Millenium Pharmaceuticals, under investigation), inhibits the ubiquitin-proteasome pathway by blocking activation of NF-jB, thereby inducing apoptosis and rendering melanoma more chemosensitive. Further studies are underway.

Biopsy technique The importance of a proper biopsy for any suspicious pigmented lesion cannot be overemphasized. As discussed earlier, depth remains the single most important prognostic factor of the primary tumor. Therefore,

50

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

adequate sampling of the primary lesion necessitates obtaining the full thickness of the lesion. Shave biopsies of any suspicious lesions are completely discouraged. Additional information that should be provided in the pathology report of a melanoma include adequacy of resection vis-a`-vis an indication of relationship of melanoma to surgical margins, presence or absence of lymphovascular or neural invasion, and presence or absence of microsatellites. At our institution, mention of the histologic cell type and presence or absence of a precursor lesion are made as well (Fig. 14).

Lymph nodes The spread of malignant cells from primary tumor to regional lymph nodes represents the pivotal step in the transformation of melanoma from having a good prognosis to having a poor prognosis. As such, the importance of unequivocally identifying deposits of tumor in a lymph node cannot be underestimated. The challenge to the pathologist is not a simple one. The prevalence of false negative and false positive results has provided the impetus to attain more sensitive and specific methods of detecting malignant melanocytes. The increasing practice of sentinel lymph node biopsies has thrust the question of how best to interpret lymph node specimens onto center stage. Histological interpretation The identification of microscopic foci, often only single cells, of melanoma within lymph nodes is daunting. Histologically, melanoma cells may resemble benign, pigment-laden histiocytes that are normally scattered throughout the lymph node. Metastatic melanoma must also be distinguished from nevus cell rests. Because these benign nevic rests characteristically reside within the nodal fibrous capsule and nodal trabecula, distinction from metastatic melanoma, which typically first drains into the subcapsular sinus, can be particularly difficult. Immunohistochemical and genetic tools have been used to facilitate sentinel node analysis of microscopic deposits. Ultimately, however, hematoxylyn and eosin histopathology remains the standard for diagnosis of melanoma, and any ancillary studies must be interpreted in this context. Immunohistochemical analysis Among the variety of molecular techniques that are used to characterize melanoma, immunohistochemistry is the oldest and most widespread. Given the temptation for over- or underdiagnosis of nodal metastatic melanoma deposits by hematoxylyn and eosin staining alone, an active search has been undertaken for immunohistochemical markers that are specific for melanoma.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

51

Fig. 14. Massachusetts General Hospital (MGH) - Malignant Melanoma Reporting Worksheet.

In general, antigenic markers may be specifically associated with malignancy or nonspecifically associated with benign and malignant lesions. Among those in the former category are MAGE-1 [79] and MAGE-3 [80]. These so-called embryonal cancer testis antigens have been found in

52

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

melanoma, but their precise prognostic significance is unknown. Better characterized, but not specific for melanoma, are the well-known molecules, S-100, HMB-45, and MART-1. S-100 is a calcium-channel binding protein that has been suggested as a tumor progression marker. The monoclonal antibody was derived from human melanoma cells, and targets a 10-kDa cytoplasmic glycoprotein portion of a transmembrane complex [81]. S-100 was initially proposed as a melanoma marker, but was subsequently found to stain benign nevic cells as well, as seen in activated junctional nevi, the dermal nevic cells in patients with HIV, blue nevi, and deep penetrating nevi. Attempts to correlate serum levels with the likelihood of micrometastatic disease yielded variable results [82]. Although its sensitivity is limited by its staining of interdigitating reticulum cells, perinodal fat, and peripheral nerves, as well as benign nevus cell aggregates, the primary value of S-100 immunohistochemical staining in lymph nodes lies in its sensitivity as a melanocyte marker. HMB-45 and MART-1 are two other common markers that are used in immunohistochemistry for lesions of melanocytic derivation. MART-1 and Melan-A decorate the gp100 antigen complex, which consists of a transmembrane protein that was initially detected in melanocytes in normal skin, retinal tissue, and melanoma. As such, gp100 is believed to serve as a melanocytic differentiation antigen. Melanoma of spindle cell morphology typically does not stain with HMB-45. Although its detection of gp100 is not specific for malignant transformation in routine use, MART-1 expression by micrometases in sentinel lymph nodes was negatively correlated with survival [83]. Similarly, tyrosinase, a membrane-bound glycoprotein that functions in melanin biosynthesis by catalysing the conversion of tyrosine to dihydroxyphenylalanine (DOPA), and DOPA to dopaquinone, was found to be a sensitive indicator of micrometastasis in sentinel lymph nodes that were negative on routine histopathological examination [83]. gp75, a similar, related antigen to gp100, is targeted by the Mel-5 immunostain [84]. Microophthalmia transcription factor (Mitf) is another antibody that was recently investigated for use in melanoma diagnosis [85]. Functioning as a transcription regulator of the tyrosinase gene, Mitf expression has been linked with prognosis in intermediate thickness melanomas [86]. Molecular diagnostic tools: polymerase chain reaction and microarray techniques Current efforts to improve the sensitivity, specificity, and convenience of lymph node screening for melanoma have focused attention on molecular analysis. Studies of the use of reverse-transcriptase polymerase chain reaction (RT-PCR) to detect presumed melanoma-specific messenger RNA in lymph nodes suggested that RT-PCR analysis can offer greater sensitivity for melanoma detection than routine histology and immunohistochemistry [87]. Moreover, a significantly greater clinical recurrence rate was observed

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

53

in patients with lymph node positivity for tyrosinase by RT-PCR [88]. Given its exquisite sensitivity, however, concerns have been raised over falsepositive results and overinterpretation of the significance of positive findings. Final assessment of the pragmatic value of RT-PCR technology for lymph node analysis awaits further experience [89]. A powerful new approach to molecular diagnosis is offered by genetic microarray techniques [90]. The global expression profile of a malignant melanoma can be characterized by generating cDNA clones to expressed fluorescent mRNA transcripts, and then applying the thousands of DNA probes onto a microarray. The ability to identify transcript profiles that are associated with malignant phenotype has been demonstrated [91]; the potential diagnostic and prognostic benefits await to be realized. Pathologic analysis of sentinel lymph nodes Based upon the premise that melanoma metastasizes to a lymphatic basin through a sequential order of individual lymph nodes, any metastatic disease within the lymphatic basin should be reflected by melanoma in the first draining lymph node. As such, this first draining lymph node serves as a sentinel for the regional lymphatics. Moreover, it follows that dissection and pathologic analysis of this sentinel lymph node should offer an effective screen for metastatic disease. The validity of the sentinel lymph node dissection procedure, however, is predicated upon accurate identification by lymphoscintigraphy and 1% lymphazurin dye of the first lymph node (or nodes) that drains the tumor. Sentinel lymph node dissection is offered to patients with intermediate thickness melanoma (1 to 4 mm), given the relatively low risk for metastasis for thinner lesions and the high risk for metastasis for thicker lesions. Various protocols for pathologically analyzing sentinel lymph nodes are practiced at different institutions. The method for handling sentinel lymph nodes adopted at our institution was derived from studying 94 patients whose 235 lymph nodes were negative by routine hematoxylyn and eosin analysis; however, in 11 of the patients the results were positive by sectioning deeper levels into the tissue block and with immunohistochemical staining [92]. Formalin-fixed sentinel lymph nodes are bisected through their hila, and each heminode is serially dissected in its entirety to yield sections that are 1 to 2 mm thick. The sections are paraffin-embedded and nine levels are taken in three groups of three; each group is separated by 80 microns. The first, fourth, and seventh levels are stained with MART-1; the second, fifth, and eighth levels are stained with hematoxylyn and eosin (H & E); the third, sixth, and ninth levels are stained with S-100. In our laboratory, the high sensitivity of the S-100 immunostain complements the high specificity of the MART-1. A single melanoma cell detected renders the lymph node as positive for metastasis, and any extracapsular invasion is noted in the report.

54

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

Staging: American Joint Committee on Cancer 2002 System Background and overview of the Tumor-Node-Metastases system Various staging systems have been devised over the years to stratify patients with melanoma according to predicted biological course and prognosis. The most widely adopted system was devised by the American Joint Committee on Cancer (AJCC), the latest version of which was established in 1997. The clinicopathologic parameters used in the AJCC system include aspects of the primary Tumor, the status of lymph Nodes, and the presence and location of any Metastases (T-N-M Staging). Evaluation of data from several institutions for more than 17,000 patients justified the new staging proposal for 2002 [93]. The tumor component of the staging system factors in the Breslow thickness as well as the Clark anatomic level. Previously, tumor thickness was a secondary prognostic factor to histologic (Clark) level of invasion, with thresholds of 0.75 mm, 1.50 mm, and 4.0 mm. The recognition that tumor thickness is a more powerful determinant of prognosis and a more reproducible histopathologic variable led to its adoption as the principal parameter in primary tumor evaluation. In thick lesions, the Clark anatomic level does not seem to offer independent prognostic information; however, in thin lesions (<1.0 mm), the histologic level provides additional prognostic data. Thin melanomas with advanced histologic invasion seem to have a worse prognosis than melanomas of comparable depth with less anatomic penetration. The spread of melanoma to lymph nodes supersedes any aspect of the primary tumor in predicting prognosis. According to the previous and current staging system, nodal involvement automatically upstages the patient to at least Stage III. Moreover, the revised staging system recognizes the distinction between nodal tumor which is detectable clinically from that which is detectable only pathologically. It stands to reason that distant metastases represent most advanced disease, and as such, patients with metastases have Stage IV disease. Previously, in transit and satellite metastases were distinguished based upon distance from primary tumor (>2 cm and <2 cm, respectively) [94]. One development in the revised system is the consolidation of in transit and satellite metastases, with the recognition that the previous distinction between the two proved arbitrary and imprecise. Synoptic pathologic highlights of the 2002 AJCC Staging System As a result of the above analysis, eleven key improvements were made to the AJCC staging system (Table 1). Four of these apply to the primary tumor. First and most significantly, ulceration is now recognized as a critical prognostic determinant. When 1284 patients were evaluated for various parameters, ulceration predicted worse survival in patients with primary and

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

55

Table 1 American Joint Cancer Committee (AJCC), cutaneous melanoma pathologic staging system 2002 Stage

Tumor (T)

Node (N)

Metastases (M)

0 IA

0 0

0 0

0

0

0

0

0

0

IIC IIIA

In situ <1.0 mm w/o ulcer; Clark IV or 1.1–2.0 mm w/o ulcer 1.1–2.0 mm w/ulcer; or 2.1–4.0 mm wo/ulcer 2.1–4.0 mm w/ulcer; or >4.0 mm w/o ulcer >4.0 mm w/ulcer Any thickness w/o ulcer

0 0

IIIB

Any thickness w/ulcer

IIIC

Any thickness Any thickness ulcer Any thickness Any thickness

IV

Any thickness

0 1–4 nodes-clin occult; path positive 1–4 nodes-clin occult; path positive or 2–3 nodes2–3 nodes-clin apparent 0 nodes; þ in transit/satellite met 1–3 nodes-clin apparent >3 met nodes or >3 matted nodes or >3 in transit met/satellite w/nodal met Any nodal status

IB

IIA IIB

w/o ulcer w/ or w/o w/ulcer w/o ulcer

0

0 0 0

Any met to skin, subcutaneous, distant node, lung, visceral or Any distant met w/elevated LDH

metastatic melanomas. By univariate analysis, ulceration presaged worse survival; when controlled for thickness, mitoses, and age, multivariate analysis predicted poorer outcome as well. Thus, ulceration was adopted in the prognostic system. Second, adjustment of the thresholds for measured depth now stratify ‘‘T’’ staging into integer millimeter divisions: (<1 mm, 1–2 mm, 2–4 mm, >4 mm). Third, and more importantly, Clark level is now more clearly subjugated to thickness as the predominant staging determinant of primary tumor. Clark microanatomic level is now only prognostically relevant in thin melanomas (<1 mm). Fourth, thick melanomas (>4.0 mm), have been downstaged from Stage III to IIC; Stage III is now reserved for regional metastatic disease. With respect to regional nodal status, the most radical development was the accommodation for sentinel lymph node data, and the distinction between clinical (macroscopic) and pathologically (microscopic) detected

56

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

metastases. Furthermore, the number of nodes involved has now replaced dimensions of the metastatic deposits in prognostic assessment. The grouping of in-transit and satellite metastases and the classification of these together as regional nodal disease represents an additional refinement to the system. The final two adjustments pertain to metastatic disease. Lung metastases are now separated from other visceral metastases as M1b, in recognition of their relatively better prognosis. Finally, serum lactate dehydrogenase is now included as a second determinant of M staging.

References [1] Crowson AN, Magro CM, Mihm MC. The melanocytic proliferations: a comprehensive textbook of pigmented lesions. New York: Wiley-Liss; 2001. [2] Sagebiel RW. The dysplastic melanocytic nevus. J Am Acad Dermatol 1989;20:496–501. [3] Clark WH Jr, Ackerman AB. An exchange of views regarding the dysplastic nevus controversy. Semin Dermatol 1989;8:229–50. [4] Rigel DS, Rivers JK, Kopf AW, et al. Dysplastic nevi. Markers for increased risk for melanoma. Cancer 1989;63:386–9. [5] Tucker MA, Halpern A, Holly EA, et al. Clinically recognized dysplastic nevi: a central risk factor for cutaneous melanoma. JAMA 1997;277(18):1439–44. [6] Albert LS, Rhodes AR, Sober AJ. Dysplastic nevi and cutaneous melanoma: markers of increased melanoma risk for affected persons and blood relatives. J Am Acad Dermatol 1990;22:69–75. [7] Clemente C, Cochran AJ, Elder DE, et al. Histopathologic diagnosis of dysplastic nevi: concordance among pathologists convened by the World Health Organization Melanoma Programme. Hum Pathol 1991;22:313–9. [8] Barnhill RI, Roush GC. Correlation of clinical and histopathologic features in clinically atypical melanocytic nevi. Cancer 1991;67:3157–64. [9] Spitz S. Melanomas of childhood. Am J Path 1948;24:591–609. [10] Weedon D, Little JH. Spindle and epithelioid cell nevi in children and adults. A review of 211 cases of the Spitz nevus. Cancer 1977;40:217–25. [11] Kaye VN, Delner LP. Spindle and epithelioid cell nevus (Spitz nevus). Natural history following biopsy. Arch Dermatol 1990;126:1581–3. [12] Kamino H, Flotte TJ, Msuloff E. Eosinophilic globules in Spitz’s nevi. New findings and a diagnostic sign. Am J Dermatopathol 1979;1:319–24. [13] Busam KJ, Barnhill RL. Pagetoid Spitz nevus. Intraepidermal Spitz tumor with prominent pagetoid spread. Am J Surg Pathol 1995;19(9):1061–7. [14] Barnhill RL, Argenyi ZB, From L, et al. Atypical Spitz nevi/tumors: lack of consensus for diagnosis, discrimination from melanoma, and prediction of outcome. Hum Pathol 1999;30(5):513–20. [15] Smith KJ, Barrett TL, Skelton HG III, et al. Spindle cell and epithelioid cell nevi with atypia and metastasis (malignant Spitz nevus). Am J Surg Pathol 1989;13:931–9. [16] Reed RJ, Ichinose H, Clark WH, et al. Common and uncommon melanocytic nevi and borderline melanomas. Semin Oncol 1975;2:119–47. [17] Sagebiel RW, Chinn EK, Egbert BM. Pigmented spindle cell nevus. Clinical and histologic review of 90 cases. Am J Surg Pathol 1984;8(9):645–53. [18] Rock B, Hood AF, Rock JA. Prospective study of vulvar nevi. J Am Acad Dermatol 1990;22:104–6.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

57

[19] Clark WH Jr, Hood AF, Tucker MA, et al. Atypical melanocytic nevi of the genital type with a discussion of reciprocal parenchymal-stromal interactions in the biology of neoplasia. Hum Pathol 1998;29:1–24. [20] Clark WH Jr, From L, Bernardino EA, et al. The histogenesis and biologic behavior of primary human malignant melanomas of the skin. Cancer Res 1969;29:705. [21] Tannous ZS, Lerner LH, Duncan LM, et al. Progression to invasive melanoma from malignant melanoma in situ, lentigo maligna type. Hum Pathol 2000;31(6):705–8. [22] Elder DE, Guerry D IV, Epstein MN, et al. Invasive malignant melanomas lacking competence for metastasis. Am J Dermatopathol 1984;6:55. [23] McGovern VJ, Mihm MC, Bailly C, et al. The classification of malignant melanoma and its histologic reporting. Cancer 1973;32:1446–57. [24] Price NM, Rywlin AM, Ackerman AB. Histologic criteria for the diagnosis of superficial spreading malignant melanoma. Cancer 1976;38:2434. [25] Clark WH, Mihm MC. Lentigo maligna and lentigo-maligna melanoma. Am J Pathol 1969;55:39. [26] Weinstock MA, Sober AJ. The risk of progression of lentigo maligna to lentigo maligna melanoma. Br J Dermatol 1987;116:303. [27] Coleman WP 3rd, Loria PR, Reed RJ, Krementz ET. Acral lentiginous melanoma. Arch Dermatol 1980;116:773–6. [28] Clark WH Jr, Elder DE, Van Horn M. The biologic forms of malignant melanoma. Hum Pathol 1986;5:443. [29] Plotnick H, Rachiamolf M, Van du Berg HJ Jr Polypoid melanoma: a virulent variant of nodular melanoma. J Am Acad Dermatol 1990;23:880–4. [30] Phillips ME, Margolis RJ, Merot Y, et al. The spectrum of minimal deviation melanoma: a clinicopathologic study of 21 cases. Hum Pathol 1986;17:796. [31] Schmoeckel C, Castro CE, Braun-Falco O. Nevoid malignant melanoma. Arch Dermatol Res 1985;277:362. [32] Wong TY, Suster S, Duncan LM, et al. Nevoid melanoma: a clinicopathological study of seven cases of malignant melanoma mimicking spindle and epithelioid cell nevus and verrucous dermal nevus. Hum Pathol 1995;26:171–9. [33] Blessing K, Grant JJ, Sanders DS, et al. Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis. J Clin Pathol 2000;53(8):591. [34] McNutt NS, Urmacher C, Hakimian J, et al. Nevoid malignant melanoma: morphologic patterns and immunohistochemical reactivity. J Cutan Pathol 1995;22:502. [35] Scalzo DA, Hida CA, Toth G, et al. Childhood melanoma: a clinicopathological study of 22 cases. Melanoma Res 1997;7(1):63–8. [36] Barnhill RLW, Flotte TJ, Fleischli M, et al. Cutaneous melanoma and atypical Spitz tumors in childhood. Cancer 1995;76:1833. [37] Conley J, Lattes R, Orr W. Desmoplastic malignant melanoma. Cancer 1971;28:914. [38] Carlson JA, Dickersin GR, Sober AJ, et al. Desmoplastic neurotropic melanoma: a clinicopathologic analysis of 28 cases. Cancer 1995;75:478–94. [39] Levene A. Equine melanotic disease. Tumori 1971;57(3):133–68. [40] Crowson AN, Magro CM, Mihm MC Jr Malignant melanoma with prominent pigment synthesis with ‘‘animal type’’ melanoma. Hum Pathol 1999;30(5):543–50. [41] Mihm MC, Clemente CG, Cascinelli N. Tumor infiltrating lymphocytes in lymph node melanoma metastases: a histopathologic prognostic indicator and an expression of local immune response. Lab Invest 1996;74:43. [42] Abernethy JL, Soyer HP, Kerl H, et al. Epidermotropic metastatic malignant melanoma simulating melanoma in situ: a report of 10 examples from two patients. Am J Dermatopathol 1994;18:1140. [43] Clark WH, Elder DE, Guerry D, et al. Model predicting survival in stage I melanoma based on tumor progression. J Natl Cancer Inst 1989;81:1893.

58

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

[44] Day CL, Mihm MC, Sober AJ, et al. Prognostic factors for melanoma patients with lesions 0.76–1.69 mm in thickness. An appraisal of ‘‘thin’’ level IV lesions. Ann Surg 1982;195:30–4. [45] Garbe C, Buttner P, Bertz J, et al. Primary cutaneous melanoma. Identification of prognostic groups and estimation of individual prognosis for 5093 patients. Cancer 1995;75: 2484–91. [46] Schuchter L, Schultz DJ, Synnestvedt M, et al. A prognostic model for predicting 10-year survival in patients with primary melanoma. Ann Intern Med 1996;125:369–75. [47] Breslow A. Thickness, cross-sectional areas and depth of invasion in the prognosis of cutaneous melanoma. Ann Surg 1970;172:902. [48] Blois MS, Sagebiel RW, Abarbanel RM, et al. Malignant melanoma of the skin. I. The association of tumor depth and type, and patient sex, age, and site with survival. Cancer 1983;52:1330–41. [49] Prade M, Bognel C, Charpentier P, et al. Malignant melanoma of the skin: prognostic factors derived from a multifactorial analysis of 239 cases. Am J Dermatopathol 1982; 4:411–2. [50] Kelly JW, Sagebiel RW, Clyman S, et al. Thin level IV malignant melanoma: a subset in which level is the major prognostic indicator. Ann Surg 1985;202:98. [51] Buttner P, Garbe C, Bertz J, et al. Primary cutaneous melanoma: optimized cutoff points of tumor thickness and importance of Clark’s level for prognostic classification. Cancer 1995;75:2499. [52] Cochran AJ. Histology and prognosis in malignant melanoma. J Pathol 1969;97:459. [53] Kopf AW, Gross DF, Rogers GS, et al. Prognostic index for malignant melanoma. Cancer 1987;59:1236–41. [54] Balch CM, Wilkerson JA, Murad TM, et al. The prognostic significance of ulceration of cutaneous melanoma. Cancer 1980;45:3012. [55] Day CL, Lew RA, Harrist TJ. Malignant melanoma prognostic factors : ulceration width. J Dermatol Surg Oncol 1984;10:23–4. [56] Clemente CG, Mihm MC, Bufalino R, et al. Prognostic value of tumor-infiltrating lymphocytes in the vertical growth phase of primary cutaneous melanoma. Cancer 1996; 77:1303–10. [57] Ronan SG, Eng AM, Briele HA, et al. Thin malignant melanomas with regression and metastases. Arch Dermatol 1987;123:1326–30. [58] Day CL, Harrist TJ, Gorstein F, et al. Malignant melanoma. Prognostic significance of ‘‘microscopic satellites’’ in the reticular dermis and subcutaneous fat. Ann Surg 1981; 194:108–12. [59] Leon P, Daly JM, Synnestvedt M, et al. The prognostic implication of microscopic satellites in patients with clinical stage I melanoma. Arch Surg 1991;126:1461–8. [60] Statius Muller MG, van Leeuwen PAM, de Lange-de Klerk ESM, et al. The sentinel lymph node status is an important factor for predicting clinical outcome in patients with stage I or II cutaneous melanoma. Cancer 2001;91:2401–8. [61] Duncan LM. Prognostic indicators in melanoma. Chapter 17 in Advances in Dermatology, Volume 15. St. Louis: Mosby, 1999. [62] Heenan PJ, Jarvis LR, Armstrong BK. Nuclear indices and survival in cutaneous melanoma. Am J Dermatopathol 1989;11:308–12. [63] Sorensen FB, Kristensen IB, Grymer F, et al. DNA level, tumor thickness, and sterological estimates of nuclear volume in stage 1 cutaneous malignant melanomas. Am J Dermatopathol 1991;13:11–9. [64] Gambini C, Casazza S, Borgiani L, et al. Counting the nucleolar organizer regionassociated proteins is a prognostic clue of malignant melanoma. Arch Dermatol 1992; 128:487–90. [65] Ramsay JA, From L, Iscoe NA, et al. MIB-1 proliferative activity is a significant prognostic factor in primary thick cutaneous melanomas. J Invest Dermatol 1995;105: 22–6.

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

59

[66] Hazan C, Melzer K, Panageas KS, et al. Evaluation of the proliferation marker MIB-1 in the prognosis of cutaneous malignant melanoma. Cancer 2002;95(3):634–40. [67] Vecchiato A, Rossi CR, Montesco MC, et al. Proliferating cell nuclear antigen (PCNA) and recurrence in patients with cutaneous melanoma. Melanoma Res 1994;4:207–11. [68] Essner R, Kuo CT, Wang H, et al. Prognostic implication of p53 overexpression in cutaneous melanoma from sun-exposed and nonexposed sites. Cancer 1998;82:309–16. [69] Clurman BE, Groudine M. The CDKN2A tumor-suppressor locus- a tale of two proteins. N Engl J Med 1998;338:910–2. [70] Monzon J, Liu L, Brill H, et al. CDKN2A mutations in multiple primary melanomas. N Engl J Med 1998;338:879–87. [71] Duncan L, Deeds J, Hunter J, et al. Down-regulation of the novel gene melastatin correlates with potential for melanoma metastasis. Cancer Res 1998;58:1515–20. [72] Johnson JP, Stade BG, Holzmann B, et al. De novo expression of intercellular-adhesion molecule 1 in melanoma correlates with increased risk of metastasis. Proc Natl Acad Sci USA 1989;86:641–54. [73] Schadendorf D, Gawlik C, Haney U, et al. Tumor progression and metastatic behavior in vivo correlates with integrin expression on melanocytic tumors. J Pathol 1993;170:429. [74] Natali PG, Hamby CV, Felding-Habermann B, et al. Clinical significance of alpha(v)beta3 integrin and intercellular adhesion omolecule-1 expression in cutaneous malignant melanoma lesions. Cancer Res 1997;57:1554–60. [75] Kageshita T, Hamby CV, Ishihara T, Matsumoto K, Saida T, Ono T. Loss of [beta]catenin expression associated with disease progression in malignant melanoma. Br J Dermatol 2001;145(2):210–6. [76] Elder DE, Rodeck U, Thurin J, et al. Antigenic profile of tumor progression stages in human melanocytic nevi and melanomas. Cancer Res 1989;49:5091–6. [77] Huang S, DeGuzman A, Bucana CD, et al. Nuclear factor-kappaB activity correlates with growth, angiogenesis, and metastasis of human melanoma cells in nude mice. Clin Cancer Res 2000;6(6):2573–81. [78] Mitsiades N, Mitsiades CS, Poulaki V, et al. Molecular sequelae of proteasome inhibition in human multiple myeloma cells. Proc Natl Acad Sci USA 2002;99(22):14374–9. [79] Chen YT, Stockert E, Chen Y, et al. Identification of the MAGE-1 gene product by monoclonal and polyclonal antibodies. Proc Natl Acad Sci USA 1994;91(3):1004–8. [80] Hofbauer GF, Schaefer C, Noppen C, et al. MAGE-3 immunoreactivity in formalin-fixed, paraffin-embedded primary and metastatic melanoma: frequency and distribution. Am J Pathol 1997;151(6):1549–53. [81] Donato R. Functional role of S100 proteins, calcium-binding proteins of the EF-hand type. Biochem Biophys Acta 1999;1450(3):191–231. [82] Acland K, Evans AV, Abraha H, et al. Serum S100 concentrations are not useful in predicting micrometastatic disease in cutaneous malignant melanoma. Br J Dermatol 2002;146(5):832–5. [83] Hochberg M, et al. Expression of tyrosinase, MIA and MART-1 in sentinel lymph nodes of patients with malignant melanoma. Br J Dermatol 2002;146(2):244–9. [84] Bahwan J. Mel-5: a novel antibody for differential diagnosis of epidermal pigmented lesions of the skin in paraffin-embedded sections. Melanoma Res 1997;7(1):43–8. [85] King R, Googe PB, Weilbaecher KN, et al. Microphthalmia transcription factor expression in cutaneous benign, malignant melanocytic, and non-melanocytic tumors. Am J Surg Pathol 2001;25(1):512–57. [86] Salti GI, Manougian T, Farolan M, et al. Microphthalmia transcription factor: a new prognostic marker in intermediate-thickness cutaneous malignant melanoma. Cancer Res 2000;60(18):5012–6. [87] Bostick PJ, Morton DL, Turner RR, et al. Prognostic significance of occult metastases detected by sentinel lymphadenectomy and reverse transcriptase-polymerase chain reaction in early-stage melanoma patients. J Clin Oncol 1999;17(10):3238–44.

60

V. Liu, M.C. Mihm / Surg Clin N Am 83 (2003) 31–60

[88] Blaheta HJ, Schittek B, Breuninger H, et al. Detection of micrometastasis in sentinel nodes by reverse transcription-polymerase chain reaction correlates with tumor thickness and is predictive of micrometastastic disease in the lymph node basin. Am J Surg Pathol 1999;23(7):822–8. [89] Morton DL, Thompson JF, Essner R, et al. Validation of the accuracy of intraoperative lymphatic mapping and sentinel lymphadenectomy for early-stage melanoma: a multicenter trial. Ann Surg 1999;230(4):453–63. [90] Bittner M, Meltzer P, Chen Y, et al. Molecular classification of cutaneous malignant melanoma by gene expression profiling. Nature 2000;406(6795):536–40. [91] Su YA, Bittner ML, Chen Y, et al. Identification of tumor-suppressor genes using human melanoma cell lines UACC903, UACC903(+6), and SRS3 by comparison of expression profiles. Mol Carcinogen 2000;28(2):119–27. [92] Yu LL, Flotte TJ, Tanabe KK, et al. Detection of microscopic melanoma metastases in sentinel lymph nodes. Cancer 1999;86(4):617–27. [93] Balch CM, Buzaid AC, Soong SJ, et al. Final version of the American Joint Committee on Cancer Staging System for cutaneous melanoma. J Clin Onc 2001;19(16):3635–48. [94] Harrist TJ, Rigel DS, Day CL Jr, et al. Microscopic satellites are more highly associated with regional lymph node metastases than is primary melanoma thickness. Cancer 1984; 53(10):2183–7.