—  SPECIALTY CONFERENCE  —

Dermatopathology

Case 7 - Epithelioid Sarcoma

Lori Erickson
Mayo Clinic College of Medicine
Rochester, MN





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History
51 year old female presented with a "lesion" on her distal upper extremity.


Case 7 - Slide 1
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Case 7 - Figure 1
Sheets of atypical cells within the dermis, focally palisading around areas of necrosis.
Case 7 - Figure 2
Atypical cells with zonal necrosis.
Case 7 - Figure 3
Atypical cells palisading around areas of necrosis.


Immunophenotype
Immunoperoxidase studies performed on paraffin embedded tissue sections show the lesional cells are positive for vimentin, cytokeratin AE1/AE3, EMA, and CD34. The cells are negative for S100 and CD31.

Diagnosis
Epithelioid sarcoma

Discussion
In 1970 Dr. Franz Enzinger described 62 cases of epithelioid sarcoma as a "peculiar form of sarcoma that has repeatedly been confused with a chronic inflammatory process, a necrotizing granuloma, and a squamous cell carcinoma". [1] He noted that similar cases had been described in the literature as a "distinctive and peculiar" variant of synovial sarcoma affecting the extensor tendon of the wrist [2] and the ring finger bearing a "striking resemblance to epithelium." [1, 3] The WHO definition of epithelioid sarcoma is: "A distinctive sarcoma of unknown lineage showing predominantly epithelioid cytomorphology, affecting mainly adolescents and young adults." [4] Included in the WHO definition is - "This tumour may be misdiagnosed as a benign lesion, especially as a benign granulomatous process." [4]

Clinical Features
The tumors occur most commonly in young adults. In Dr. Enzinger's original report the median age at diagnosis was 26 years. [1] The age range is quite broad with cases reported in infants [5], children [6, 7, 8] and in the elderly. [9] Males are affected more commonly than females. [10] In Chase and Enzinger's series of 241 cases about 20% were associated with trauma. [10] The tumors most commonly involve the finger, hand, wrist, and forearm. [10] The lower extremities, particularly the pretibial region, knee, as well as the buttocks and thigh, shoulder and arm, and distal lower extremities can also be involved. [10] Involvement of the trunk and head and neck occurs, but is uncommon with the exception of the scalp. [10, 11, 12, 13, 14, 15, 16] Mucosal sites including the tongue have been reported. [17] The genital areas may also be involved. [18, 19, 20] including the vulva and perineum, [19, 20] scrotum, [18] and penis. [21, 22, 23]

Clinically, the tumors are usually firm, painless, relatively slow growing single or multiple nodules which may ulcerate with raised margins. The tumors range in size from a few millimeters to greater than 15 cm. [10] The tumors often are located in the dermis, subcutis and can grow along aponeuroses. These tumors clinically can be mistaken for reactive conditions including ulcers and granuloma annulare as well as palmar fibromatosis when they are located on the distal upper extremity. Tumors on proximal sites may be mistaken for other sarcomas and in genital areas are mistaken for Peyrone's disease. When the tumors ulcerate they can clinically be mistaken for indurated ulcers, abscesses, and ulcerated squamous cell carcinomas.

A "proximal-type" epithelioid sarcoma was described as a "distinctive aggressive neoplasm showing rhabdoid features." [24] These tumors tend to occur in axial locations and tend to behave more aggressively than conventional epithelioid sarcomas. In the study be Guillou et al in 1997, these tumors were described as having overlapping features with malignant extrarenal rhabdoid tumors. [24] Whether these tumors represent a variant of malignant extrarenal rhabdoid tumor or are a more aggressive variant of epithelioid sarcoma occurring in proximal sites is not clear. These tumors often occur in the pelvis, perineum and genitalia, are usually deep seated, and occur in adults. [10, 19, 24, 25, 26, 27, 28, 29]

Microscopic Features
Histologically, the tumors consist of irregular nodular masses or large, deeply acidophilic polygonal cells merging with spindle cells, and often associated with prominent hyalinized collagen. [1] The distinct nodular arrangement and the areas of central degeneration and necrosis and the epithelioid cytomorphology of the cells are characteristic features. The tumors are often solitary at first operation, but may be multiple. Multiple nodules are more common in recurrent tumors than in primary tumors. [1] Necrosis is very common. When multiple necrotizing tumor nodules fuse together, the tumor has a "geographic" pattern which gives the appearance of "garland-like" ands of viable tumor separated by areas of necrosis. [1]

The cellular constituency ranges from large polygonal cells with deeply eosinophilic cytoplasm which cytologically can resemble rhabdoid cells to prominent spindle cells. In Enzinger's original series the "deeply acidophilic polygonal cells" merged with spindle cells. [1] The cells merge imperceptibly, lacking the distinctive biphasic pattern seen in epithelioid sarcoma. The cells with spindle morphology are more prominent in early and primary lesions, while recurrent lesions often show more epithelioid cells. [1] The cells also lack significant cytologic atypia and cellular pleomorphism is minimal. However, the tumor cells may show more cytologic atypia in recurrences. Metastatic tumors often show less cellular differentiation and more extensive necrosis than primary and recurrent tumors. [1] Tumors with predominance of spindle cells often lack the typical necrobiotic nodular epithelioid pattern. [30, 31] The spindle cells are described as "deceptively bland fibrohistiocytic and myoid cells arranged in a fibroma-like or dermatofibroma-like pattern with an affinity for osseous involvement." [30] Tumors may also show discohesion of the large epithelioid cells and hemorrhage into spaces giving it an angiomatoid or angiosarcoma-like appearance. [1, 32, 33] In Enzinger's original series, about 13% of the cases had calcification, and 8% had osteoid or bone formation. [1]

Tumors described as "proximal-type" epithelioid sarcoma are usually identified in the deep soft tissues and have prominent epithelioid or rhabdoid features with marked cytologic atypia and a multinodular growth pattern. [24] Necrosis is commonly seen, but the classic granuloma-like pattern of classic epithelioid sarcoma is uncommon. [24]

Behavior
In Enzinger's original report of 62 cases, follow-up was available in 54 cases (87%). [1] The tumors were described as showing a slow, relentless clinical course with frequent recurrence (85%) and late metastasis (30%). [1] With an average follow-up of 7 years (range 1 to 26 years), 12 of the 54 (22%) patients with follow-up information had died of disease or complications of disease, and 17 (31%) of the others had suffered recurrences or metastases or both. [1] In Chase and Enzinger's subsequent retrospective review of 241 cases, follow-up was available in 202 cases (84%). [10] The recurrence rate was 77%, and the metastatic rate was 45%. Lymph nodes (48%) and lungs (25%) were the most common initial sites of metastases, followed by scalp, bone, brain, liver, and pleura [10] However, the most common metastatic site overall was lung which accounted for 51% of metastases. [10] Features associated with aggressive behavior included a proximal or axial tumor location, increased size and depth, hemorrhage, mitotic activity, necrosis, and vascular invasion. [10] Favorable prognostic factors included younger age, location in distal extremities, and occurrence in females aged 10-49. [10]

Immunophenotype
Immunopositivity for keratin is characteristic of epithelioid sarcoma and very helpful in the diagnosis. The tumors are usually positive for low and high molecular weight keratin, epithelial membrane antigen, and vimentin (Tables 1 and 2). [32, 33, 34, 35, 36] The epithelioid areas generally show more keratin immunoreactivity as compared to the spindled areas. The majority of tumors are positive for CD34. S100, CEA, factor VIII, CD31, and LCA are usually negative. [32, 33, 34, 35, 36]

Table 1. Immunohistochemical studies of epithelioid sarcoma (positive/ total cases).

Study Keratin Cam5.2 CK7 CK20 EMA Vimentin CD34 Other
Chase [35]24/32
Chase [10]34/44 CEA (5/13), S100 (1/12), HFVIII (0/11)
Humble [34] 8/8 2/8 0/8 7/8 6/6 3/8 S100 (0/7), 34BE12 (3/8), HHF35 (2/5)
Laskin [36] 7/54 5/57 CK14 (25/50), g-catenin (4/27), calretinin (8/40), p63 (2/15), CD117 (5/29), CD10 (1/33)
Miettinen [32] 82/87 17/77 69/72 74/74 39/75 CK19 (72%), 34BEH12 (48%), muscle specific actin (41%), CD31 (7%, focal, not membranous), Factor VIII (0)
Manivel [37]13/14 8/14 14/14 LCA (0/14), myoglobin (0/14), Factor VIII (0/14), S100 (1/14), desmin (1/14), CEA (4/14), actin (4/14)
Arber [38]3/3 3/3 0/3 3/3 Factor VIII (0/3), S100 (1/3, focal), HMB45 (0/3), MSA (0/3), SMA (0/3), desmin (0/3)
Kato [39]11/11 11/11 11/11 6/11 CA125 (10/11), CEA (2/11)
Abbreviations: 34BE12 (keratin 1, 5, 10, 14,/15), Cam5.2 (keratin 8, 18), MSA (muscle specific actin), SMA (smooth muscle actin)

Table 2. Immunohistochemical studies of epithelioid sarcoma variants – angiomatoid, fibroma-like, and large cell rhabdoid (positive/ total cases).

Variant (Study) Cam 5.2 CK 7 CK 20 CK 5/6 EMA Vimentin CD 34 Other
Angiomatoid (Miettinen [32]) 7/8 2/7 7/7 8/8 5/8 MSA (2/7), CD31 (2/8, focal, not membranous), Factor VIII (0/8)
Angiomatoid (Laskin [36]) 1/6 0/2 CK14 (2/7), g-catenin (3/7), calretinin (1/4), p63 (1/2), CD117 (0/3), CD10 (0/4)
Fibroma-Like (Miettinen [32]) 6/7 2/5 4/4 6/7 3/6 CK19 (7/7), 34BEH12 (6/7), muscle specific actin (0/6), Factor VIII (0)
Fibroma-Like (Laskin [36]) 7/54 1/6 CK14 (1/1), g-catenin (1/5), calretinin (0/3), p63 (0/2), CD117 (0/4), CD10 (0/3)
Large Cell/Rhabdoid (Miettinen [32]) 9/9 3/9 9/9 9/9 4/8 CK19 (7/8), 34BEH12 (4/8), muscle specific actin (2/8), Factor VIII (0)
Large Cell/Rhabdoid (Laskin [36]) 2/5 1/1 CK14 (3/6), g-catenin (1/5), calretinin (3/6), p63 (0/1), CD117 (0/1), CD10 (0/1)

34BE12 (keratin 1, 5, 10, 14,/15)
Cam5.2** (keratin 8, 18)

Tumors reported as "proximal-type" epithelioid sarcoma cases generally show the same immunophenotype as classic epithelioid sarcomas. In a study of 18 of these tumors, all but one case were positive for keratin, EMA and vimentin. [24] Desmin was positive in 10 of 16, CD34 in 8 of 16, HMB45 in 3 of 13, CEA in 1 of 10, with S100 and CD31 being negative in all cases. [24] A study of 20 cases of showed all were positive for vimentin and cytokeratin, with 17 (85%) positive for EMA, 9 (45%) positive for CD34, 5 (25%) positive for CD99, and 3 (15%) positive for muscle markers, either desmin or smooth muscle actin. [27] Other markers such as S100, neurofilament, NSE, synaptophsin and CD56 were positive in 12 (60%) of cases. [27]

Ultrastructure
Epithelioid sarcomas show a spectrum of cells from epithelial-type cells with abundant intermediate filaments, desmosome-like cell junctions and small intercellular spaces surrounded by microvilli to spindled cells. [40] The intermediate filaments often form paranuclear masses compatible with the prominent cytoplasm and epithelioid appearance histologically. [41]

Genetic Features
Epithelioid sarcomas have been shown by flow cytometry to have a diploid or hyperploid (near diploid) DNA content which has been suggested to correspond to the relatively long clinical course and low-grade malignant nature of epithelioid sarcoma. [42] A number of cytogenetic abnormalities have been detected in epithelioid sarcomas including a case with der(22)t(18;22)(q11;p11.2) and a number of other clonal abnormalities including numerical (-3, -4, +7, -13, -14, -16, -18, +20, -22) and structural (8p+, 9p+, 12p+, i(21q)) aberrations as well as i(18q) [43] The authors suggested that since the breakpoint at 18q11 is similar to that for synovial sarcoma, this finding may suggest relationship between epithelioid sarcoma and synovial sarcoma. [43] A study evaluating the presence of loss of heterozygosity (LOH) of chromosome 22q in tumor DNA from 13 epithelioid sarcomas showed LOH was in 6 of 10 (60%) of the informative cases. [44] Chromosome 22q carries the locus of the neurofibromatosis 2 (NF2) gene. [44]

A case of proximal-type epithelioid sarcoma was analyzed by comparative genomic hybridization and found to have chromosomal gain of 5q32-qter, 12q24-qter, and 22q. [28] A report of two children and one young adult with extremity sarcomas demonstrating an aggressive clinical behavior and histologic compatible with a deep-seated epithelioid sarcoma or with a malignant rhabdoid tumor. The tumors were positive for both vimentin and epithelial antigens and negative for desmin. The DNA profile was diploid in all 3 cases. In one case, a trisomy of chromosome 2 was found in the tumor cells, and the authors comment this may suggest a relationship with rhabdomyosarcomas. [45]

Differential Diagnosis
The title of Dr. Enzinger's original manuscript "Epithelioid Sarcoma: A Sarcoma Simulating a Granuloma or a Carcinoma" reflects the similarity of this tumor with a variety of conditions, both inflammatory and neoplastic. Entities in the differential diagnosis of epithelioid sarcoma include inflammatory conditions such as granuloma annulare, rheumatoid nodule, necrobiosis lipoidica, and granulomatous infections. Sarcomas with epithelioid features such as epithelioid malignant peripheral nerve sheath tumor (MPNST), synovial sarcoma, and epithelioid angiosarcoma are in the differential diagnosis as well as melanoma and ulcerated squamous cell carcinoma.

Bland cytomorphology of most epithelioid sarcomas can be confused with necrobiotic granulomas such as granuloma annulare and rheumatoid nodule. The cells in epithelioid sarcoma are usually more distinct and epithelioid than those in granuloma annulare and rheumatoid nodule. Although mitotic activity is usually relatively low in epithelioid sarcoma, mitotic activity can be seen in granuloma annulare. [46] Thus, the presence of mitotic activity cannot be relied upon to separate these entities. Immunoperoxidase studies can be very useful in differentiating these lesions in difficult cases. Epithelioid sarcoma is characteristically positive for cytokeratin and is often positive for EMA, markers negative in necrobiotic granuloma. [47]

Epithelioid sarcoma, particularly spindle cell or fibroma-like variant is described as having "deceptively bland fibrohistiocytic and myoid cells arranged in a fibroma-like or dermatofibroma-like pattern" and often lack the typical necrobiotic nodular epithelioid pattern. [30, 31] This variant in particular needs to be distinguished from fibromatoses. Epithlioid sarcoma has been mistaken for Duputren's contracture on the hand [48, 49], and Peyronie's disease in the genitalia. [21, 50] The immunopositivity for cytokeratin is very helpful in identifying epithelioid sarcoma in these cases.

Sarcomas with epithelioid features must also be differentiated from epithelioid sarcoma. Synovial sarcoma has often been confused with epithelioid sarcoma, but epithelioid sarcoma does not show the characteristic biphasic pattern of synovial sarcoma nor does it show pseudoglandular structures. Rather, the epithelioid cells in epithelioid sarcoma merge with the spindled cells. Also, the location of the tumor in the dermis and involving the distal upper extremities is more common for epithelioid sarcoma than for synovial sarcoma. However, small synovial sarcomas have been reported in the hands and feet. [51] In difficult cases, immunostains may be helpful in differentiating these tumors as synovial sarcomas are usually positive for cytokeratin 7 and negative for CD34, and epithelioid sarcomas are usually negative or show only focal staining for cytokeratin 7 and positive for CD34. [32] Immunostains can also be helpful in separating epithelioid sarcoma from epithelioid MPNST as epithelioid MPNST stains strongly for S100 [52], a marker which is usually negative in epithelioid sarcoma. [34] Epithelioid sarcoma is also characteristically positive for cytokeratin, a marker negative in epithelioid MPNST.

Epithelioid angiosarcoma can mimic the angiomatoid variant of epithelioid sarcoma. [33, 53] However, epithelioid sarcoma usually occurs in younger patients and shows less cytologic atypia than angiosarcoma. The characteristic nodular growth pattern and granulomatous features are also more characteristically seen in epithelioid sarcoma than in angiosarcoma. In difficult cases immunoperoxidase studies can be very helpful in separating these entities. Epithelioid angiosarcoma can also be positive for cytokeratin. [54] Although many epithelioid sarcomas show positivity for CD34, they are negative for CD31 and factor VIII. [32, 37] Epithelioid sarcoma-like hemangioendothelioma, a low-grade vascular tumor, mimics epithelioid sarcoma due to the nested and sheet like growth pattern, the rounded to slightly spindled cells showing eosinophilia, and the immunopositivity for cytokeratin. [55] These tumors lack well defined multicellular vascular channels and hemorrhage, but some cases show intracytoplasmic vacuolization suggestive of lumen. Although recurrences were noted, distant metastases were not identified. Similar to epithelioid sarcoma, these tumors tended to occur in young adults and were positive for cytokeratin and vimentin, but they also showed positivity for CD31 and FLI-1 and were negative for CD34. [55] Thus, the immunophenotype is particularly helpful in differentiating these tumors from epithelioid sarcoma.

Epithelioid sarcomas must also be differentiated from other carcinomas, particularly ulcerated squamous cell carcinomas. Epithelioid sarcoma lacks the keratin pearls seen in squamous cell carcinoma. Additionally, squamous cell carcinomas usually emanate from the overlying epidermis, a feature not seen in epithelioid sarcoma. Furthermore, squamous cell carcinomas show dysplasia of the associated epidermis, a finding not present in epithelioid sarcoma. The co-expression of cytokeratin with vimentin and CD 34 in epithelioid sarcoma is also helpful in separating epithelioid sarcoma from squamous cell carcinoma.

In conclusion, epithelioid sarcomas are uncommon tumors, but are in the differential diagnosis of common entities, including common benign entities such as granuloma annulare, granulomatous infections, and fibromatoses as well as malignant neoplasms such as sarcomas with epithelioid features and carcinomas. The tumors tend to occur in the extremities of young adults and can have a slow and relentless clinical course. A high index of suspicion is needed to make the diagnosis of epithelioid sarcoma, and a panel of immunoperoxidase studies is helpful in the evaluation of these tumors.

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