- Email: [email protected]
Immunoperoxidase staining of cytoplasmic immunoglobulins
Immunoperoxidase staining of cytoplasmic immunoglobulins A diagnostic aid in distinguishing cutaneous reactive lymphoid hyperplasia from malignant lymphoma Ronald J. Barr, M.D., Nora C. J. Sun, M.D., M.Sc., and Don Friday King, M.D.* Irvine and Torrance, CA A method for staining cytoplasmic immunoglobulins utilizing an immunoperoxidase technic on paraffin-embedded tissue was used to examine two cutaneous lesions. On routine hematoxylin-eosin staining, one lesion exhibited what appeared to be a mixed population of mature cell types and was therefore interpreted as reactive lymphoid hyperplasia, whereas the other lesion showed a uniform population of immature cells and was interpreted as a malignant lymphoma. Immunoperoxidase staining supported these interpretations since the reactive lesion showed polyclonal IgG.\ and K staining, and the malignant lymphoma monoclonal staining with IgG.\. In selected material, immunoperoxidase staining can distinguish a truly mixed population of cell types (probably benign) from a monoclonal population of cells exhibiting either uniform or mixed morphologic configurations associated with B lymphocyte transformation (probably malignant). (J AM ACAD DERMATOL 3:58-62, 1980.)
Distinguishing reactive lymphoid hyperplasia of the skin (pseudolymphoma, lymphocytoma cutis) from true malignant lymphoma is often difficult. Although certain histologic criteria have been established to aid in their differentiation, considerable controversy remains. I.:! A modification of a previously described immunoperoxidase method From the Section of Dermal Patholo gy and Histochemi stry. Departrnent of Dermatology. University of California at Irvine. and the Department of Pathology, Harbor/UCLA Medical Center. Torrance. Supported in part by the Southern California Dermatology Foundation. Reprint reque sts to: Dr. Ronald J. Barr, Section of Dermal Pathology and Histochemistry. UCI Medical Center, 101 City Drive South, Orange, CA 926681714-634-5556. -Currenlly with the Department of Dermatology. New York University,
58
was employed to study intracellular (cytoplasmic) immunoglobulins in paraffin-embedded tissue." Since this method can differentiate many polyclonal from monoclonal B lymphocytic infiltrates, it may also separate many of those that are benign from those that are malignant. CASE REPORT The patient, a 72-year-old man, presented with a 3-month history of erythematous papules and plaques primarily on the face and trunk . During this time, the patient also noted a 7-kg weight loss, increasing . Iethargy , and increasing abdominal girth. Four years prior to admission, he developed a scaly plaque on the left shoulder which persisted. The patient gave a history of "psoriasis" for many years. Clinical examination revealed multiple erythematous, indurated, focally 0190-9622/80/070058+05S00.50/0 © 1980 Am Acad Derrnatol
Volume 3 Number I July, 1980
lmmunoperoxidase staining of immunoglobulins
59
Fig. 1. Cutaneous biopsy of neck, revealing a relatively monomorphic cellular infiltrate consisting of angular or elongated infolding nuclei and indistinct nucleoli. Note that the cytoplasm is inconspicuous. (lmmunoperoxidase stain with anti-x as the specific antiserum, and counterstained with hematoxylin, x 630. *) *Figs. t and 2 were taken under exactly the same conditions to illustrate that these lymphocytes conta in monoclonal 11. light chain. A similar result was obta ined from the study of heavy chain s. The lymphocytes contained IgG only.
scaly plaque s, papules, and a 1.3-cm nodule on the nape of the neck. Cervical and axillary lymph nodes were enlarged, and there was moderate hepatosplenomegaly. Important laboratory findings included: hemoglobin, 12.5 gm/IOO ml, hematocrit, 38, and decreased platelets. Bone marrow biopsy exhibited diminished iron and moderate lymphocytosis. A cutaneous punch biopsy was taken from the plaque on the left shoulder and interpreted as reactive lymphoid hyperpl asia. Additional biopsies from the nodule on the neck and a left axillary lymph node were interpreted as malignant lymphoma, poorly differentiated lymphocytic type (small cleavedcell type of Lukes-Collins classification) , The patient was begun on chlorambucil and prednisone. At follow-up, 7 months after initial presentation, the patient was alive on maintenance therapy. The cutaneous lesions had almost completely resolved .
MATERIALS AND METHODS
Light microscopy Sections were fixed in 10% neutral buffered formaldehyde solution, proce ssed routinely, and embedded in
paraffin. Section were cut at 4-5 I-'- and stained with hematoxylin-eosin.
Intracellular immunoglobulin study by immunoperoxidase method Formalin-fixed, paraffin-embedded skin and lymph node biopsy specimens were processed as described above. A modification of a previously reported indirect immunoperoxidase method was used." The deparaffinized tissue was treated with 3% H2 0 2 in methanol to block endogenous peroxidase activity. After washing in phosphate buffer, each slide was flooded with one of the following rabbit antihuman immunoglobulins: y, a, JL, 0, E, A, K and antilysozyme. An adequate wash was performed after this and subsequent reagents. The tissue was sequentially treated with the following: goat antirabbit 19, rabbit antihorseradish peroxidase, and horseradish peroxidase. The slide was finally stained with 3,3'-diaminobenzidine tetrahydrochloride (3,3'DAB) in TRIS buffer and hydrogen peroxide and counterstained with hematoxylin. The positive reaction product was dark brown and the nucleus blue. The
Journal of the American Academy of Dermatology
60 Barr et al
Fig. 2. A consecutive tissue section from the same tissue block as Fig. 1. Note diffuse positive staining indicated by a gray background (dark brown color on the slide) surrounding each nucleus (arrows). (lmmunoperoxidase stain with anti-A as the specific antiserum, and counterstained with hematoxylin, x630.) specificity of the antisera was checked by double immunodiffusion. (All antisera were purchased from Behring Diagnostics, Somerville, NJ, and chemicals from Sigma Chemical Co., St. Louis, MO.)
RESULTS Microscopic observations Cutaneous biopsy, left shoulder. The hematoxylin-eosin-stained section exhibited mild epidermal atrophy with effacement of the rete ridges. Separated from the epidermis by a thin, uninvolved band of papillary dennis (grenz zone), there was a diffuse, focally nodular infiltrate composed of what were interpreted as lymphocytes and histiocytes. In a few foci, occasional multinucleated cells could be identified. The blood vessels, presumably postcapillary venules, showed some increase in branching and endothelial cell proliferation. The adnexal structures, blood vessels, and reticular dermal collagen were viable and intact. The infiltrate extended into the superficial subcutaneous fat. Cutaneous biopsy, neck. Examination of the sections exhibited an essentially normal epidermis
with a subjacent grenz zone. All levels of the dennis, as well as the subcutaneous fat, were replaced by a multinodular infiltrate. The infiltrate consisted of an essentially homogeneous population of mononuclear cells (Fig. I). On high-power magnification and under oil immersion, many of these cells had one or more nuclear invaginations and scant cytoplasm. Lymph node biopsy. Examination of the hematoxylin-eosin-stained sections showed destruction of the normal nodal architecture, with replacement by an essentially homogeneous population of mononuclear cells identical to those seen in the neck biopsy specimen. The tumor was interpreted as a poorly differentiated lymphocytic lymphoma (Rappaport classification)" or small cleaved B cell (follicular center cell) lymphoma (Lukes-Collins classification)." Immunoperoxidase studies Cutaneous biopsy, left shoulder. Examination showed positive results with anti-y, A, and K indicating a polyclonal population. Cutaneous biopsy, neck. Examination showed
Volume 3 Number I July. 1980
positive results only with anti-y and 'A indicating a monoclonal population producing IgG-'A (Figs. 1 and 2). Lymph node. Examination showed positive results with anti-y and 'A. DISCUSSION
The following diagnostic classification and definitions for lymphoid infiltrates in the skin have been established based on routine microscopic examination2 . ; : 1. Probably benign: Defined by a mixed population of mature cells, e.g., lymphocytes and histiocytes. 2. Probably malignant: Defined by a uniform population of immature (cytologically atypical) cells. 3. Unpredictable: Defined by all other combinations, e .g., mixed mature and immature or uniform mature. This classification has been found to be quite useful; however, types 1 and III infiltrates are sometimes a source of error. These errors can now be understood in light of recent advances in the immunologic approach to malignant lymphomas. Lukes et al," and subsequently confirmed by others.P-" showed that most non-Hodgkiri's lymphomas are of B cell origin. Excluding mycosis fungoides and Sezary syndrome, this applies to the skin as well. The normal B lymphocytes are capable of undergoing a series of morphologic transformations after an appropriate antigenic stimulus. The stimulated small B lymphocytes appear as small cleaved cells, large cleaved cells, small noncleaved cells, ·Iarge noncleaved cells, immunoblasts, and plasma cells, with plasma cell as the end cell. G The immunoblast may also revert to a small B lymphocyte and the cycle repeated. The small and large cleaved cells and small and large noncleaved cells are the components of secondary follicles; therefore, they are also called follicular center cells. Lukes et al G•8 showed that most nonHodgkin's lymphomas are follicular center cell lymphomas, and they often represent a proliferation of one of these morphologic expressions. For example, poorly differentiated lymphocytic Iyrnphoma represents a proliferation of small cleaved cells. Recently, van den Tweel et all I suggested
Inununoperoxidase staining of immunoglobulins
61
that some lymphomas (so-called composite lymphomas) may show more than one morphologic expression, although a single cell type usually predominates. Sun et al" also demonstrated that morphologically different cell types actually carried the same intracellular immunoglobulin. Therefore, some infiltrates that may be perceived as being of mixed cell types by conventional hematoxylin-eosin-stained section may in reality be a monoclonal cell proliferation exhibiting a variety of morphologic configurations. It follows that type I (probably benign) and type III lesions (unpredictable) may include monoclonal proliferations (probably malignant) and polyclonal proliferations (probably benign). The immunoperoxidase method for demonstrating intracellular immunoglobulin may allow for this distinction. The current case is of particular interest in that it illustrates the great difficulties associated with interpreting lymphoid infiltrates, and the usefulness of immunoperoxidase staining in supporting light microscopic interpretations. The diagnosis of reactive lymphoid hyperplasia was seriously questioned when the patient was found to have a systemic lymphoma; however, immunoperoxidase staining clearly defined the benign infiltrate as being polyclonal and the malignant infiltrate as monoclonal. Patients with lymphoma or leukemia may develop reactive lymphoid hyperplasia during the course of their disease, and separating this from recurrence of the malignant neoplasm is important for both therapeutic and prognostic reasons. Evaluations based on immunoperoxidase staining must be undertaken with certain precautions . Not all benign or malignant infiltrates of the skin are of B cell origin. T cell or null cell infiltrates and granulocytic sarcomas can and do occur. Although rare, it is possible that some lymphomas may be polyclonal and some benign infiltrates monoclonal. 8 The amount of imrnunoperoxidasestainable cytoplasmic immunoglobulin also varies somewhat depending on cell type. Small B lymphocytes contain little cytoplasmic immunoglobulin, whereas large, noncleaved lymphocytes contain large amounts. II The actual procedure itself may result in a certain number of false-positives or false-negati ves. The commercially purchased antisera have to be relatively purified; otherwise,
62
Journal of the American Academy of Dermatology
Barr et af
nonspecific reactions may give false-positive results. The hydrogen peroxide may decompose easily and give a false-negative result. This reagent, therefore, has to be kept refrigerated and tightly closed. A set of controls with known positive and negative results should be included. In summary, immunoperoxidase staining for cytoplasmic immunoglobulins appears to be a valuable aid in interpreting selected cutaneous lymphoid infiltrates. Although studies are currently underway to determine the precise implication of monoclonal cutaneous lymphoid infiltrates, we believe that most will subsequently be proved to be malignant lymphomas. Like all other diagnostic criteria, immunoperoxidase staining of cytoplasmic immunoglobulins must be correlated with additional clinical and histologic data. It is recommended that all type I or type III lesions be evaluated utilizing immunoperoxidase staining. Those patients exhibiting a monoclonal infiltrate should undergo a thorough hematologic workup and be carefully followed.
2. Fisher ER, Park EJ, Wechsler HL: Histologic identification of malignant lymphoma cutis. Am J Clin Pathol
We thank Mr. Ed Davis, Department of Pathology, Harbor/UCLA Medical Center, for his assistance with the photomicrographs.
10.
REFERENCES
II.
I. Caro WA, Helwig EB: Cutaneous lymphoid hyperplasia. Cancer 24:487-502, 1969.
65:149-158, 1976. 3. Sun NCJ, Fishkin BG, Nies KM, et al: Lyrnphoplasmacytic myeloma: An immunological, immunohistochemical, and electron microscopic study. Cancer 43:2268-2278, 1979. 4. Afroudakis AP, Liew CT, Peters RL: An immunoperoxidase technique for the demonstration of the hepatitis B surface antigen in human liver. Am J Clin Pathol 65:533-539, 1976. 5. Rappaport H: Tumors of the hematopoietic system, ill Atlas of tumor pathology. Washington, DC, 1966, Armed Forces Institute of Pathology, sect. 3, fascicle 8. 6. Lukes RJ, Collins RD: Immunologic characterization of human malignant lymphomas. Cancer 34: 1488-1503,
1974. 7. Barr RJ, Shneidman DW, Graham JH: Pseudomalignant
8.
9.
and pseudobenignant lesions of the skin and subcutaneous tissues, ill Moschella SL, editor: Dermatology update. New York, 1979, Elsevier, North-Holland, Inc., pp. 273-323. Lukes RJ, Taylor CR, Parker JW, et al: A morphologic and immunologic surface marker study of 299 cases of non-Hodgkin's lymphomas and related leukemias. Am J Pathol 90:461-485, 1978. Nathwani BN, Kim H, Rappaport H, et al: NonHodgkin's lymphomas: A clinicopathologic study comparing two classifications. Cancer 41:303-325, 1978. Born-van Noorloos AA, Splinter TAW; van Heerde P, et al: Surface marker and functional properties of nonHodgkin's lymphoma cells in relation to histology. Cancer 42:1804-1817, 1978. van den Tweel JG, Lukes RJ, Taylor CR: Pathophysiology of lymphocyte transformation. A study of so-called composite lymphomas. Am J Clin Pathol 71:509-520,
1979.
Distinguishing reactive lymphoid hyperplasia of the skin (pseudolymphoma, lymphocytoma cutis) from true malignant lymphoma is often difficult. Although certain histologic criteria have been established to aid in their differentiation, considerable controversy remains. I.:! A modification of a previously described immunoperoxidase method From the Section of Dermal Patholo gy and Histochemi stry. Departrnent of Dermatology. University of California at Irvine. and the Department of Pathology, Harbor/UCLA Medical Center. Torrance. Supported in part by the Southern California Dermatology Foundation. Reprint reque sts to: Dr. Ronald J. Barr, Section of Dermal Pathology and Histochemistry. UCI Medical Center, 101 City Drive South, Orange, CA 926681714-634-5556. -Currenlly with the Department of Dermatology. New York University,
58
was employed to study intracellular (cytoplasmic) immunoglobulins in paraffin-embedded tissue." Since this method can differentiate many polyclonal from monoclonal B lymphocytic infiltrates, it may also separate many of those that are benign from those that are malignant. CASE REPORT The patient, a 72-year-old man, presented with a 3-month history of erythematous papules and plaques primarily on the face and trunk . During this time, the patient also noted a 7-kg weight loss, increasing . Iethargy , and increasing abdominal girth. Four years prior to admission, he developed a scaly plaque on the left shoulder which persisted. The patient gave a history of "psoriasis" for many years. Clinical examination revealed multiple erythematous, indurated, focally 0190-9622/80/070058+05S00.50/0 © 1980 Am Acad Derrnatol
Volume 3 Number I July, 1980
lmmunoperoxidase staining of immunoglobulins
59
Fig. 1. Cutaneous biopsy of neck, revealing a relatively monomorphic cellular infiltrate consisting of angular or elongated infolding nuclei and indistinct nucleoli. Note that the cytoplasm is inconspicuous. (lmmunoperoxidase stain with anti-x as the specific antiserum, and counterstained with hematoxylin, x 630. *) *Figs. t and 2 were taken under exactly the same conditions to illustrate that these lymphocytes conta in monoclonal 11. light chain. A similar result was obta ined from the study of heavy chain s. The lymphocytes contained IgG only.
scaly plaque s, papules, and a 1.3-cm nodule on the nape of the neck. Cervical and axillary lymph nodes were enlarged, and there was moderate hepatosplenomegaly. Important laboratory findings included: hemoglobin, 12.5 gm/IOO ml, hematocrit, 38, and decreased platelets. Bone marrow biopsy exhibited diminished iron and moderate lymphocytosis. A cutaneous punch biopsy was taken from the plaque on the left shoulder and interpreted as reactive lymphoid hyperpl asia. Additional biopsies from the nodule on the neck and a left axillary lymph node were interpreted as malignant lymphoma, poorly differentiated lymphocytic type (small cleavedcell type of Lukes-Collins classification) , The patient was begun on chlorambucil and prednisone. At follow-up, 7 months after initial presentation, the patient was alive on maintenance therapy. The cutaneous lesions had almost completely resolved .
MATERIALS AND METHODS
Light microscopy Sections were fixed in 10% neutral buffered formaldehyde solution, proce ssed routinely, and embedded in
paraffin. Section were cut at 4-5 I-'- and stained with hematoxylin-eosin.
Intracellular immunoglobulin study by immunoperoxidase method Formalin-fixed, paraffin-embedded skin and lymph node biopsy specimens were processed as described above. A modification of a previously reported indirect immunoperoxidase method was used." The deparaffinized tissue was treated with 3% H2 0 2 in methanol to block endogenous peroxidase activity. After washing in phosphate buffer, each slide was flooded with one of the following rabbit antihuman immunoglobulins: y, a, JL, 0, E, A, K and antilysozyme. An adequate wash was performed after this and subsequent reagents. The tissue was sequentially treated with the following: goat antirabbit 19, rabbit antihorseradish peroxidase, and horseradish peroxidase. The slide was finally stained with 3,3'-diaminobenzidine tetrahydrochloride (3,3'DAB) in TRIS buffer and hydrogen peroxide and counterstained with hematoxylin. The positive reaction product was dark brown and the nucleus blue. The
Journal of the American Academy of Dermatology
60 Barr et al
Fig. 2. A consecutive tissue section from the same tissue block as Fig. 1. Note diffuse positive staining indicated by a gray background (dark brown color on the slide) surrounding each nucleus (arrows). (lmmunoperoxidase stain with anti-A as the specific antiserum, and counterstained with hematoxylin, x630.) specificity of the antisera was checked by double immunodiffusion. (All antisera were purchased from Behring Diagnostics, Somerville, NJ, and chemicals from Sigma Chemical Co., St. Louis, MO.)
RESULTS Microscopic observations Cutaneous biopsy, left shoulder. The hematoxylin-eosin-stained section exhibited mild epidermal atrophy with effacement of the rete ridges. Separated from the epidermis by a thin, uninvolved band of papillary dennis (grenz zone), there was a diffuse, focally nodular infiltrate composed of what were interpreted as lymphocytes and histiocytes. In a few foci, occasional multinucleated cells could be identified. The blood vessels, presumably postcapillary venules, showed some increase in branching and endothelial cell proliferation. The adnexal structures, blood vessels, and reticular dermal collagen were viable and intact. The infiltrate extended into the superficial subcutaneous fat. Cutaneous biopsy, neck. Examination of the sections exhibited an essentially normal epidermis
with a subjacent grenz zone. All levels of the dennis, as well as the subcutaneous fat, were replaced by a multinodular infiltrate. The infiltrate consisted of an essentially homogeneous population of mononuclear cells (Fig. I). On high-power magnification and under oil immersion, many of these cells had one or more nuclear invaginations and scant cytoplasm. Lymph node biopsy. Examination of the hematoxylin-eosin-stained sections showed destruction of the normal nodal architecture, with replacement by an essentially homogeneous population of mononuclear cells identical to those seen in the neck biopsy specimen. The tumor was interpreted as a poorly differentiated lymphocytic lymphoma (Rappaport classification)" or small cleaved B cell (follicular center cell) lymphoma (Lukes-Collins classification)." Immunoperoxidase studies Cutaneous biopsy, left shoulder. Examination showed positive results with anti-y, A, and K indicating a polyclonal population. Cutaneous biopsy, neck. Examination showed
Volume 3 Number I July. 1980
positive results only with anti-y and 'A indicating a monoclonal population producing IgG-'A (Figs. 1 and 2). Lymph node. Examination showed positive results with anti-y and 'A. DISCUSSION
The following diagnostic classification and definitions for lymphoid infiltrates in the skin have been established based on routine microscopic examination2 . ; : 1. Probably benign: Defined by a mixed population of mature cells, e.g., lymphocytes and histiocytes. 2. Probably malignant: Defined by a uniform population of immature (cytologically atypical) cells. 3. Unpredictable: Defined by all other combinations, e .g., mixed mature and immature or uniform mature. This classification has been found to be quite useful; however, types 1 and III infiltrates are sometimes a source of error. These errors can now be understood in light of recent advances in the immunologic approach to malignant lymphomas. Lukes et al," and subsequently confirmed by others.P-" showed that most non-Hodgkiri's lymphomas are of B cell origin. Excluding mycosis fungoides and Sezary syndrome, this applies to the skin as well. The normal B lymphocytes are capable of undergoing a series of morphologic transformations after an appropriate antigenic stimulus. The stimulated small B lymphocytes appear as small cleaved cells, large cleaved cells, small noncleaved cells, ·Iarge noncleaved cells, immunoblasts, and plasma cells, with plasma cell as the end cell. G The immunoblast may also revert to a small B lymphocyte and the cycle repeated. The small and large cleaved cells and small and large noncleaved cells are the components of secondary follicles; therefore, they are also called follicular center cells. Lukes et al G•8 showed that most nonHodgkin's lymphomas are follicular center cell lymphomas, and they often represent a proliferation of one of these morphologic expressions. For example, poorly differentiated lymphocytic Iyrnphoma represents a proliferation of small cleaved cells. Recently, van den Tweel et all I suggested
Inununoperoxidase staining of immunoglobulins
61
that some lymphomas (so-called composite lymphomas) may show more than one morphologic expression, although a single cell type usually predominates. Sun et al" also demonstrated that morphologically different cell types actually carried the same intracellular immunoglobulin. Therefore, some infiltrates that may be perceived as being of mixed cell types by conventional hematoxylin-eosin-stained section may in reality be a monoclonal cell proliferation exhibiting a variety of morphologic configurations. It follows that type I (probably benign) and type III lesions (unpredictable) may include monoclonal proliferations (probably malignant) and polyclonal proliferations (probably benign). The immunoperoxidase method for demonstrating intracellular immunoglobulin may allow for this distinction. The current case is of particular interest in that it illustrates the great difficulties associated with interpreting lymphoid infiltrates, and the usefulness of immunoperoxidase staining in supporting light microscopic interpretations. The diagnosis of reactive lymphoid hyperplasia was seriously questioned when the patient was found to have a systemic lymphoma; however, immunoperoxidase staining clearly defined the benign infiltrate as being polyclonal and the malignant infiltrate as monoclonal. Patients with lymphoma or leukemia may develop reactive lymphoid hyperplasia during the course of their disease, and separating this from recurrence of the malignant neoplasm is important for both therapeutic and prognostic reasons. Evaluations based on immunoperoxidase staining must be undertaken with certain precautions . Not all benign or malignant infiltrates of the skin are of B cell origin. T cell or null cell infiltrates and granulocytic sarcomas can and do occur. Although rare, it is possible that some lymphomas may be polyclonal and some benign infiltrates monoclonal. 8 The amount of imrnunoperoxidasestainable cytoplasmic immunoglobulin also varies somewhat depending on cell type. Small B lymphocytes contain little cytoplasmic immunoglobulin, whereas large, noncleaved lymphocytes contain large amounts. II The actual procedure itself may result in a certain number of false-positives or false-negati ves. The commercially purchased antisera have to be relatively purified; otherwise,
62
Journal of the American Academy of Dermatology
Barr et af
nonspecific reactions may give false-positive results. The hydrogen peroxide may decompose easily and give a false-negative result. This reagent, therefore, has to be kept refrigerated and tightly closed. A set of controls with known positive and negative results should be included. In summary, immunoperoxidase staining for cytoplasmic immunoglobulins appears to be a valuable aid in interpreting selected cutaneous lymphoid infiltrates. Although studies are currently underway to determine the precise implication of monoclonal cutaneous lymphoid infiltrates, we believe that most will subsequently be proved to be malignant lymphomas. Like all other diagnostic criteria, immunoperoxidase staining of cytoplasmic immunoglobulins must be correlated with additional clinical and histologic data. It is recommended that all type I or type III lesions be evaluated utilizing immunoperoxidase staining. Those patients exhibiting a monoclonal infiltrate should undergo a thorough hematologic workup and be carefully followed.
2. Fisher ER, Park EJ, Wechsler HL: Histologic identification of malignant lymphoma cutis. Am J Clin Pathol
We thank Mr. Ed Davis, Department of Pathology, Harbor/UCLA Medical Center, for his assistance with the photomicrographs.
10.
REFERENCES
II.
I. Caro WA, Helwig EB: Cutaneous lymphoid hyperplasia. Cancer 24:487-502, 1969.
65:149-158, 1976. 3. Sun NCJ, Fishkin BG, Nies KM, et al: Lyrnphoplasmacytic myeloma: An immunological, immunohistochemical, and electron microscopic study. Cancer 43:2268-2278, 1979. 4. Afroudakis AP, Liew CT, Peters RL: An immunoperoxidase technique for the demonstration of the hepatitis B surface antigen in human liver. Am J Clin Pathol 65:533-539, 1976. 5. Rappaport H: Tumors of the hematopoietic system, ill Atlas of tumor pathology. Washington, DC, 1966, Armed Forces Institute of Pathology, sect. 3, fascicle 8. 6. Lukes RJ, Collins RD: Immunologic characterization of human malignant lymphomas. Cancer 34: 1488-1503,
1974. 7. Barr RJ, Shneidman DW, Graham JH: Pseudomalignant
8.
9.
and pseudobenignant lesions of the skin and subcutaneous tissues, ill Moschella SL, editor: Dermatology update. New York, 1979, Elsevier, North-Holland, Inc., pp. 273-323. Lukes RJ, Taylor CR, Parker JW, et al: A morphologic and immunologic surface marker study of 299 cases of non-Hodgkin's lymphomas and related leukemias. Am J Pathol 90:461-485, 1978. Nathwani BN, Kim H, Rappaport H, et al: NonHodgkin's lymphomas: A clinicopathologic study comparing two classifications. Cancer 41:303-325, 1978. Born-van Noorloos AA, Splinter TAW; van Heerde P, et al: Surface marker and functional properties of nonHodgkin's lymphoma cells in relation to histology. Cancer 42:1804-1817, 1978. van den Tweel JG, Lukes RJ, Taylor CR: Pathophysiology of lymphocyte transformation. A study of so-called composite lymphomas. Am J Clin Pathol 71:509-520,
1979.