Synovial hemangioma: A report of 20 cases with differential diagnostic considerations

Synovial Hemangioma: A Report of 20 Cases With Differential Diagnostic Considerations

KENNETH DEVANEY, MD, TUYETHOA AND DONALD E. SWEET, MD

N. VINH, MD,

hemangioma by histologic features, there are some lesions, such as PVNS, that may even he confused by pathologists with synovial hemangioma. Moreover, it has been suggested by some that PVNS and synovial hemangioma may be related lesions (L. C. Johnson, personal communication, November 199 1). The present review was undertaken both to describe the clinicopathologic features of a group of synovial hemangiomas and to explore what relationship, if any, mighl. exist between synovial hemangioma and PVNS.

True synovial-based bemangiomas are uncommon lesions and, as such, may enter the differential diagnosis of other lesions encountered more frequently in clinical practice, including pigmented villonodular synovitis and traumatic hemarthrosis. The consultation files of the Armed Forces Institute of Pathology were searched for benign vascular lesions diagnosed as synovial or bursal hemangiomas submitted between the years 1960 and 1985; 20 cases of synovial hemangioma were identified. The patients ranged in age from 9 to 49 years at the time of presentation (average age, 25 years). Sixty-five percent of the patients were male; 35% were female. Presenting symptoms included pain and swelling (31%), pain alone (31%), and a painless mass (31%). Affected regions included the knee (60%). the elbow (300/o), and the finger (10%). In 65% of cases the lesion was confined to the intra-articular synovium; in 30% of cases the hemangioma was located in a bursa adjacent to a joint. One case was located largely within the joint cavity but had an area of extension into the suprapatellar recess. The dominant histologic patterns included cavernous hemangioma (50%), lobular capillary hemangioma (25%), arteriovenous hemangioma (ZOO/o), and venous hemangioma (5%). One lesion (which had been incompletely excised) was removed in its entirety 3 months after the initial subtotal resection; otherwise, none of the patients studied developed recurrent disease. The clinical diagnosis of hemangioma was made in 22% of cases, while an initial pathologic diagnosis of hemangioma was reached in 67% of cases. Pathologic differential diagnostic considerations include nonspecific synovitis/bursitis, pigmented villonodular synovitis, nodular synovitis, and organizing hemorrhage. A relationship between synovial bemangioma and pigmented villonodular synovitis was not suggested by this analysis of our material. HUM PATHOL 24:737-745. Copyright 0 1993 by W.B. Saunders Company

MATERIALS

AND METHODS

The consultation files of the .4rmed l~orces Institute 01 Pathology were searched for cases of IxGgn \ ascular lesions of the intra-articular synovium and bursa subnlitted between the years 1960 and 1985; ?6 cases were identified.
RESULTS

Synovial-based lesions that prove on microscopic examination to be localized hemangiomas are unusual in clinical practice; synovial hemangiomas may enter into the clinical differential diagnosis of mass lesions, such as pigmented villonodular synovitis (PVNS), lipoma arborescens. juxta-articular myxoma, and synovitis of unknown etiology. While many of these differential diagnostic possibilities are usually separable from synovial

Clinical The 20 patients ranged in age from 9 to 49 years at the time of presentation (average age. 25 years). Male patients predominated, comprising 65% of the total; 35% of the patients were female. Among the 15 patients in whom race was specified, 86% were white, 7% were black, and 7% were Asian. Symptoms reported at the time of presentation included pain and swelling (3 1 %%), pain alone (31%), and a painless mass (:3 1%); a single patient (5%) carried the diagnosis of recurrent intraarticular hemorrhage. The duration of symptoms ranged from 1 month to 8 years (average, 2.0 veal-s). A history of previous trauma was elicited from three patients. Twelve patients (60%) either presented during childhood (216 years of age) or reported symptoms dating back to childhood. In none of the 20 patients were adjacent or distant cutaneous hemangiomas reported. Specific mention was made of aspiration of bloody fluid from the affected site in four patients; in one of

FI-OHIthe Lkpartment of Orthopedic Pathology, Armed Forces Institute of l’atholo~~, Washington. DC: and the Department of Parholog), Brrwn C~niversity, Rhode Island Hospital, Providence. Rl. ,kceptcd f’or publication December 8, 1992. L’resenccd in part at the Fall 11192 meeting of the Amcl-ican Societ) of (Xnical Pathologists.

Addr-es\ ~(lr-1-espondcnce and reprint requests to Kenneth Devanep, MD, Department of Pathology. Brown University, Rhode Island Hospiral, 593 Eddy St, Providence, RI 02903. Copyright (0 1993 1,~ W.B. Saunders (:ompany

0046-X1 77 ‘~~:~~‘~-ro7-oocln$s.o0/0 737

Volume 24, No. 7 (July 1993)

HUMAN PATHOLOGY

these patients three “bloody taps” of the knee joint spanned a 3-year period leading to eventual surgical exploration and definitive diagnosis. Sites of involvement included the knee (60%), the elbow (30%), and the finger (interphalangeal joint of the thumb in one patient, proximal interphalangeal joint of the middle finger in the other) (10%). In 65% of cases (13 patients) the synovial hemangioma was contained within the synovial space. In 30% of cases the vascular lesion was found within a structure identified at the time of surgery as a bursal sac. In one patient the synovial hemangioma largely involved the synovial cavity but extended into the adjacent suprapatellar recess as well. One patient (the patient in whom the hemangioma involved both the joint space and the suprapatellar recess) had an initial subtotal resection of the soft tissue (suprapatellar recess) component. Symptoms persisted postoperatively, however, and the synovial component was excised 3 months after the initial procedure. None of the remaining patients reported symptoms suggestive of recurrent disease (average follow-up period, 9.4 years); one patient died of unrelated causes (bronchopneumonia complicating viral pneumonia) 2 years after excision of the synovial hemangioma.

FIGURE 1. An onteroposterior roentgenogram of the left knee region of a 13_year-old boy with a synovial hemangioma showing a vague soft tissue density in the vicinity of the joint space but no discrete lesions. This is the characteristic radiologic appearance of synovial hemangioma on plain films.

Radiologic The radiologic studies (available in seven cases), in general, were not of great use in pinpointing a specific etiology. In the majority of cases (four) no specific abnormalities could be found on plain films of the affected joints. In two cases ill-defined intra-articular soft tissue masses were found (Fig 1); in one of these cases the adjacent distal femur and proximal tibia showed a mild degree of demineralization suggestive of disuse. On plain films the seventh case showed an intra-articular soft tissue mass with internal densities interpreted as phleboliths. Arthrograms were available in three cases. In two of these cases the arthrograms failed to reveal a discrete intra-articular lesion; in the third case an irregular filling defect in the vicinity of the suprapatellar recess was identified (Fig 2). Pathologic Grossly, the pathologic specimens ranged in size from 0.8 cm to 6.0 cm (average, 4.1 cm). A villus architecture was noted grossly in five (25%) of the specimens. Nine specimens (45%) were described as grossly pigmented. A discrete nodular or sessile lesion was identified in 14 of the cases (70%), while six of the lesions were diffuse (30%). All 20 lesions arose within either the synovial space or an adjacent bursal structure; none of these cases showed involvement of the adjacent bone or skeletal muscle. The principal microscopic patterns were variable. In 50% of the lesions (10 cases) a proliferation of dilated thin-walled vascular spaces dominated the histologic findings; accordingly, cavernous hemangioma was diagnosed (Fig 3). The next most frequent pattern was that of a grouped arrangement of capillary sized vessels 738

associated with large “feeder” vessels. This lobular capillary (pyogenic granuloma type) hemangioma appeared in 25% of cases (five patients). An admixture of thickwalled muscular vessels. some with elastic laminae and some without, was found in 20% of the cases (four lesions); accordingly, arteriovenous hemangioma was diagnosed in these instances (Fig 4). Finally, a single lesion showed a proliferation of thick-walled muscular vessels that lacked elastic laminae. This lesion was diagnosed as a venous hemangioma. None of the cases manifested microscopic features associated with aggressive behavior; specifically, neither nuclear hyperchromasia/pleomorphism nor mitotic activity was found in the 20 lesions (with the exception of focal areas of papillary endothelial hyperplasia (PEH), marked by a mild degree of hyperchromasia and scattered mitotic figures). One lesion (a nodular intra-articular hemangioma) was partially infarcted; otherwise, areas of focal necrosis (as might be encountered in an angiosarcoma) were not found. Intravascular thrombosis appeared in seven of the lesions; in two of them PEH was seen. In both of the latter cases the PEH appeared within vascular spaces, a component of an abnormal proliferation of vascular elements. Plexiform vascular lesions were not seen. Two lesions contained phleboliths (in one instance these phleboliths were seen on preoperative radiographic studies as well). Microscopic hemosiderin deposition appeared in 11 cases (including the nine lesions in which gross pigmentation was noted). The distribution of hemosiderin was highly variable; in some cases it was primarily superficial, while in others it was principally found deep in the lesion some distance from the synovial lined surface (Fig 5). Depending on the case, the hemosiderin deposits were either diffuse or focal.

SYNOVIAL

HEMANGIOMA

(Devaney et al)

FIGURE 2. An arthrogram of the left knee of an 18-year-old man with a synovial hemangioma, showing an irregular filling defect in the vicinity of the suprapatellar recess.

from tendon sheaths in our classification of synovial hemangioma, preferring to diagnose these lesions as hemangiomaa of tendons or tendon sheaths; thi5 is based on the fact that such lesions are not actually confined by a synovial structure “I and the ob5er\,ation that some of the clinicopathologic features of these lesions differ from those of intra-articular or bursal hemangiomas; the hemangiomas of tendon sheaths a1.t‘ enccnmtered most often in the distal upper extremitv and are less likely to be described as pigmented vilius structures grosslv.‘~“~” tie also exclude from the group 01’ true synovial hemangiomas soft tissue lesions that irnolve, in addition to synovial structures, other regions, such as the intramedullary compartment of the bone, s’keletal muscle, or subcutis; in our practice such lesions are considered to be examples of angiomatosis. Ix This distinction has great prognostic import, as soft tissue angiomatosis so defined is usually a large deforming lesion affecting a significant portion of an extremity with XI extremely high likelihood of local recurrence following attempts It appears that some earlie at surgical resection.‘X.“’ reports of synovial hemangioma included some instances of lesions that we would classify as angiomatosis, partiall) explaining a higher incidence of local recurrence in those reports than was found in our study material.“, ‘-“’ The clinical diagnosis of localized synovial hemangioma is often elusive; in our cases the clinical diagnoses proffered included PVNS (33%1, bursitis (22%), hemangioma (22%), and mass, not otherwise specifiecl (22%). The radiologic difierential diagnosis of a sof’t tissue mass within the synovial space includes synovial hemangioma, PVNS.“‘-” and lipoma ;Irhorescms (Table l).“‘.“’ Identification of structures sqggestivc of phle-

Lymphoid follicles were not seen scattered throughout the stroma associated with the vascular elements. A myxoid stromal change (particularly in a perivascular location) likewise was not noted in our material. Mature adipocytes (a minor microscopic feature not appreciated grossly) were interspersed with the proliferating vessels in three cases. Sheets of macrophages were not encountered in any of the 20 lesions; in the cases with associated deposits of hemosiderin pigment this material was largely located within the stroma, with only scattered pigment-laden macrophages interspersed. Similarly, stromal multinucleated giant cells were not a feature of these cases of svnovial hemangioma.

DISCUSSION Whereas incolvement of the extremities by hemangiomas is rather commonplace, actual synovial based hemangiomas are rare lesions. Bouchut is general]) credited with publishing one of the first descriptions of a vascular lesion alTecting the joint; in that case, the knee.’ In the early 20th century Benrlett and Cobe) reported five personal and 24 previously published cases of synovial hemangioma and provided the first comprehensive clinicopathologic study of this family of lesions.’ In subsequent years approximately 120 additional cases of synovial hemangioma have been reported.“-“’ In broad terms synovial hemangiomas may be defined as benign vascular lesions arising from any structure lined by synovium, including the intra-articular region, from bursal spaces, and from tendon sheaths.“’ In our practice we do not include vascular lesions arising

739

HUMAN PATHOLOGY

Volume 24, No. 7 (July 1993)

FIGURE 3. Synovial hemangioma, covernous type, with papillary fronds of synovium that are marked by a proliferation of gaping, thin-walled vessels filled with red blood cells. (Hematoxylin-eosin stain; magniftcation X7.5)

boliths within the lesion may be helpful in suggesting a vascular tumor. such as synovial hemangioma, but this sign was found in only one of our patients. While the radiologic differential diagnosis of a defined soft tissue mass in the vicinity of a bursal structure often leads to consideration of a ‘nonspecific bursitis as well as synovial hemangioma, such a soft tissue mass also might prompt consideration of other juxta-articular lesions, including benign processes (such as juxta-articular myxoma)‘” and malignant lesions (such as synovial sarconla),2’i which have a predilection for involvement of this region. The finding of a mild degree of osteoporosis of the long

bones adjacent to the affected joint in one of our patients is a nonspecific finding suggestive of disuse, not surprising in view of the patient’s complaint of chronic pain and (presumed) disinclination to use the extremity. Arthrography may demonstrate a filling defect in some patients with synovial hemangioma (as it did in one patient in our series), but this technique is imperfect; even the florid lesions of PVNS may be overlooked on arthrography.‘” While not used for diagnostic purposes in the patients in our series, it may be that computed tomography or magnetic resonance scanning may be of some aid in delineating the extent of the lesion. Likewise,

FIGURE 4. SYnovial hemangioma, arteriovenous type, in which thick-walled muscular vessels both with and without well-developed elastic laminae are prominent. (Elastic stain; magnification X75.)

SYNOVIAL

FIGURE 5.

HEMANGIOMA

>Ee.._(_

Synovial hemangioma, lobular capillary type, in which deposits of hemosiderin pigment accentuate the lobular architecture of the lesion: sheets of macrophages associated with the deposition of hemosiderin pigment are not a feature of synovial hemangioma. (Iron stain; magnifi-

;;;g::.,\i * s-h“-’ ‘g,: ‘.$ :‘::*; L‘t’F ‘7 ’ . *T+\ :.,C $ p_:. .,’ ,~ .;r..~.l-‘~ ._. 2’,-_. .‘ z. . _=” l ‘. .I.

L x !.&-_z, :‘I ‘?

J?s--?-,_.I. ( -,

&Y..*.~_-&%_

-,

y::,

b’>.,*,ijpy.‘.w ” *2 * -,.

angiogl-aphy was not used in the evaluation of any of our patients; an earlier report describes the utility of angiography in delineating the extent of the lesion in a patient with a synovial hemangioma of the knee,” but nlost physicians have had no experience with the use of this modality in the diagnosis of synovial hemangioma. From a pathologic standpoint localized synovial hemangioma is less likely to lead to differential diagnostic problems (Table 1); initial diagnoses of our material included hemangioma (67%), PVNS (1 I%), bursitis/synovitis. not further subclassified (1 ‘I%), and hematoma (5%). The synovium has a basic underlying vasculature of its own; thus, reactive or hyperplastic lesions (such as a nonspecific synovitis) that accentuate this normal pattern of vessels should not be misinterpreted as hemangiomas; reactive vessels are sometimes surromnded by a perivascular myxoid change within the stroma, a finding not noted in the true synovial hemangiomas (Fig 6). In some true synovial hemangiomas the sectioning of three-dimensional papillary synovial fronds in two dimensions occasionally led referring pathologists to overlook the vascular nature of the lesions and diagnose

TABLE 1.

(Devaney et al)

a nonspecific synovitis. Spaces lined on either side by synovial cells (and thus normally filled with synovial fluid) may be confused with the immediately subjacent dilated vascular channels of a cavernous hemangioma. Should confusion persist, positive immunohistochemical staining of the lining cells for factor VIII-related antigen may be of some use in confirming their endothelial nature. Positive factor VIII staining, however, does not permit separation of organizing thrombus from a true hemangioma; this distinction remains an architectural/ light microscopic one.L’7 In terms of prognosis the most significant of the histologic differential considerations is PVNS. a lesion with a significant risk of local recurrence that greatly exceeds the risk of local recurrence of synovial hemangioma.“x-‘“’ Whereas PVNS was traditionally considered to be a reactive lesion,“,‘“‘~‘~” some more recent observations (including histologic, cytogenetic, and flow cvtometric data) have been advanced to su port the classification of PVNS as a true neoplasnl.‘34.. Y7~J”In its early stages PVNS may appear relatively vascular, but with a critical difference from synovial hemangioma: the deep stroma in PVNS is filled with a sheet-like proliferation of histiocytes (both with and without cytoplasmic deposits of hemosiderin) and multinucleated giant cells, a pattern not found in synovial hemangioma (Fig 7). As the papillary synovial fronds become more exuberant as the lesion progresses, an appearance mimicking subsurface vascular spaces may be produced. These spaces, however, are lined by synovial cells and not by endothelial cells; again, the presence in the deep tissues of sheets of histiocytes and multinucleated giant cells serves to distinguish PVNS both from synovial hemangioma and from posttraumatic synovitis or ~lonspecific synovitis. The deposition of hemosiderin I hat lends the lesions of PVNS their brown coloring grossly is not restricted

Differential Diagnosis: Localized Synovial Hemangioma

741

HUMAN PATHOLOGY

Volume 24, No. 7 (July 1993)

FIGURE 6. Synovial frond from a lesion diagnosed as nonspecific synovitis; the normal vasculature of synovium is accentuated here by a perivascular myxoid change within the stroma. a finding not noted in true synovial hemangiomas. (Hematoxylin-eosin stain; magnification X75.)

lining cells and subintimal cells with production of siderosomes and, ultimately, hemosiderin was described. We interpret these observations not as evidence of a common underlying pathogenesis, but rather as a similar response in different disease states to the same stimulus, namely, hemorrhage. Historically, microscopic features (such as the density of endothelial cells”“) and clinical features (such as age of onset of the lesion”‘) have been cited as criteria for distinguishing true neoplasms of vascular origin from hamartomas. In our practice we recognize a frequent overlap of microscopic appearances between the two types of lesions and so do not attempt to distinguish vascular malformations from true benign neoplasms on histologic grounds. We use the definition of hemangioma advanced by Enzinger and Weiss, namely, that of a benign (nonreactive) process marked by an increase in the number of vessels; these vessels may appear histologically “normal” or “abnormal.““’ With regard to the distinction from reactive lesions, a history of trauma was elicited in only three of our 20 patients, making such an association unlikely. From a histologic vantage point, patterns, such as lobular capillary hemangioma, arteriovenous hemangioma, and venous hemangioma, are unlikely to have resulted frotn organization of a remote focus of hemorrhage. While scattered dilated spaces indeed may be found in an organizing hemorrhage, the finding of large, cavernous, thin-walled spaces in the lesions diagnosed as cavernous hemangiomas is interpreted as evidence of a hemangioma, not a reactive lesion. Within the group of synovial bursal hemangiomas we distinguish between nodular or sessile localized hemangiomas (14 cases) and diffuse hemangiomas (six cases). In this context the descriptor “diffuse” refers to diffuse involvement of the joint space or the bursa, not to a vascular lesion involving multiple tissues, such as

to those lesions; as seen in our material, hemosiderin deposits may be prominent in some instances of synovial hemangioma and also may be found in both hemophilic (coagulopathy-related) and nonhemophilic joint disease.““.‘” In posttraumatic hemosiderosis of the synovium the hemosiderin pigment may be both superficial and deep. The distribution of pigment in our cases of synovial hemangioma was variable: superficial (centered about the synovial layer) in some, deep to the synovium in others, and in both regions in still others. Thus, the simple pattern of deposition of hemosiderin pigment did not, of itself, allow distinction between these diagnostic possibilities. Posttraumatic lesions are encountered with much greater frequency than are true synovial hemangiomas. Organizing thrombus, particularly when applied to the surface of a villus frond, may simulate a true hemangioma (Fig 8); in the case of organizing hemorrhage, however, an associated vascular malformation is not identified. Papillary endothelial hyperplasia is an uncommon finding both in true synovial hemangioma and in organizing thrombus (Fig 9)“; when encountered in the absence of an accompanying vascular lesion, PEH is best interpreted as an uncommon type of organization within a thrombus (Fig 9). The nature of lesions diagnosed as hemangiomas is open to some questions: Are we identifying true neoplasms or, in some instances, are we merely recognizing hamartomatous (nonneoplastic) vascular proliferations! Moreover, could some “hetnangiomas” identified later in life actually represent posttraumatic lesions, again, a nonneoplastic process? Ultrastructurally, similarities have been found between synovial tissues from rabbits suffering from experimentally induced hemarthrosis’” and from humans suffering from posttraumatic hemarIn each throsis,“” PVNS,““,“5 and synovial hemangioma.” of these reports phagocytosis of erythrocytes by synovial 742

SYNOVIAL

HEMANGIOMA

(Devaney et al)

FIGURE 7. An early lesion of PVNS showing broad villi in which the underlying vasculature is prominent; here, however, the stroma is filled by a profusion of mononuclear histiocytes and multinucleated giant cells, a feature not seen in synovial hemangioma. (Hematoxylin-eosin stain; magnification X30.)

hone. ,joint. and skeletal muscle. In our opinion, such a lesion would be better classified as a form of angiomatosis. The relationship, if any, between repeated intraarticular hemorrhage and the subsequent development of PVNS has been an area of occasional discussion and debate (L.. C. Johnson, personal communication, November 199 1). With regard to synovial hemangioma in particular, the finding of hemarthrosis in association with synovial hemangioma has been repeatedly tlemonstrated”~“‘; neither in our material nor in previously published reports, however, has the subsequent

development of PVNS been demonstrated. I( would seem, therefore, that convincing evidence camlot be presented to support the notion of sy~unkl hemangioma as a precursor lesion for PVNS.
FIGURE 8. Posttraumatic hemorrhage following a twisting injury of the knee with internal derangement; here, organizing thrombus is applied to the surface of a villus frond and may simulate a true synovial hemangioma. (Hematoxylin-eosin stain; magnification X75.)

743

HUMAN PATHOLOGY

Volume 24, No. 7 (July 1993)

FIGURE 9. Papillary endothelial hyperplasio in an organizing intra-articular hemorrhage; in the absence of an associated vascular malformation the finding of PEH should not be misinterpreted as evidence of synovial hemongioma. (Hemotoxylin-eosin stain; magnification x240.)

PVNS. Moreover, synovial hemangiomas typically arise in children and young adults, age groups that antedate the typical a e group of large series of patients with PVNS,%%,,:‘“.. $ 4 Drawing on our experience and previously published reports, then, the following stereotypic clinicopathologic picture of synovial hemangioma may be constructed: the typical patient is a child or young adult who presents with a (with a slight m a 1e predominance) swollen, painful knee or elbow. The complaint often is chronic, with reports of previous relapses and remissions. On physical examination a tender spongy or firm mass may be palpable; the size of the mass may decrease with elevation of the extremity. Aspiration of the lesion often yields bloody fluid. Radiologic studies often are unrevealing, although a vague soft tissue mass may be seen in some cases on plain films of the affected joint. Clinical considerations often will include an internal derangement of cartilage, nonspecific synovitis, and PVNS. The pathologic specimen may be pigmented and grossly mimic PVNS. The microscopic features, however, are sufficiently distinctive to allow the pathologist to reach a correct diagnosis of a benign vascular lesion. Once the impression of a vascular lesion has been formed, it is incumbent on the pathologist to establish by correlation of histologic with clinical/operative findings whether the lesion is restricted to the synovial-based tissues (synovial hemangioma) or whether it involves adjacent tissues, such as the intramedullary space of bone or skeletal muscle (angiomatosis). This distinction is important, as true synovial hemangioma defined in this manner is virtually always cured by complete local excision; angiomatosis, in contrast, has a high incidence of local recurrence postsurgery.“,”

REFERENCES I. d‘Hopita1

Bouchut E: ‘I‘umeur erectile (Paris) 29:379. 1 X56

dr I’articttlation

du getrcm. (Lotte

8. tm-scn IJ, txme.

J Bottr,Joint

01 the

b)ttgwi;tt

twn-

t 960

9. Fotws~ ,J, Staple I‘M’: Svttovi;tl hett~m~icutt;t 01 the ktwrI)emont~atiot~ by at-thrc~~raph~ :tttd at-tuiograpltv. At11 ,J Koentg:ettot 11?:51?-516. 1971 11. UutmettKA: ;\ cattw 01 ~t~t’oncotts tli~rgtiosi~ viIlot~odtttar ayttcnitis. ,J (:litt Pathol 29: 1 i-2 1, 1076

01 pigrtwtttrtl

12. Wyntle-Kohct-ts CK, Andersott Cl. Tttrmo .AhI. ct .tl: Swo\iat haetrtangioma of thr kttre: I.ight atrd rlec-troti tttic rest epic litttlings. J Pathol 1”3:217-23.5. 1977 IS. Mclnernev I). I’at-k Whl: Tltet-rttogt-;tptlit aawstttrttt of \\novial hetnmgioma. Olin Kadiot L’!l:lW172. I !)7X 14. EttrirtgetFM, b!eiss SW: Benign tutnon and ttttttot..like Ivsions of blood vrssrts. itt Soft Tisstw Tttntors (et1 2). St I.ottis. MO. Mosby. I98X, pp ~89-532

Surg

17. Bate TH: Hettiartgiotttat,t :x4: 101. IO!). t 95-i

of the tettdott

\hrath.,J

Bortc Joint

1% Howat .4.J, (:atnphell I’F.: rltrgiotn~ttosta: .4 \a~ ul;tr- trtalfot-mation of it&tic y md ctlildltootl-Krpo~t of’ I7 C~WI.I’athc)lo~~ I!): 377.38” -3 1087 20. Dot-wat-t KH, (;ettattt Illi. ~Jolrtrston WI 1, ct ‘11: I’igtnrttted villonodular sytiovitia 01 \)ttovial joint\:. Clinic;il. pathologic, dlld r;idiotogic

744

Lttrdt-y KM: Hettrmgiotna Surg 5 IA: 1910-I212.

fcatttrea.

AJK Ant J Krwtttgrttol

I-lS:X77-X85.

t 984

SYNOVIAL

HEMANGIOMA

745

(Devaney et al)