General
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• Epithelioid sarcomas (ES) are rare, slow growing sarcomas with a protracted clinical course that typically occur in distal extremities of young adults, see Soft tissue chapter
  • First described in 1970 by Enzinger as epithelioid or spindled cells in a multilobular granuloma-like pattern with central hyalinization or necrobiosis (Cancer 1970;26:1029)
• Proximal-type epithelioid sarcomas (PES), which occur in vulva, were later described as aggressive tumors occurring in proximal body sites, which tend to be composed exclusively of epithelioid cells, often with rhabdoid morphology (Am J Surg Pathol 1997;21:130)

Terminology
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• Proximal-type epithelioid sarcoma terminology is frequently used in conjunction with malignant rhabdoid tumor (PES/MRT, Am J Surg Pathol 1989;13:848), but some authors consider them to be distinct entities

Epidemiology
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• Younger women (3rd to 5th decades)
• Rarely reported during pregnancy

Sites
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• Vulva, including labia majora, clitoris, labia minora, mons and Bartholin's glands

Clinical features
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• Usually presents as painless, rapidly enlarging tumor

Diagnosis
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• Diagnosis requires high index of suspicion and a battery of immunohistochemical stains

Radiology
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• MRI usually reveals extent of the tumor, is essential for treatment planning (J Gynecol Oncol 2008;19:202)

Prognostic factors
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• Tumor associated mortality of 75-100% but early surgical resection with adequate margins may lead to a better outcome
• No definite prognostic indicators identified to date
• Local recurrence is common despite negative surgical margins
• 60-75% develop distant metastasis

Case reports
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• 23 year old woman (Gynecol Oncol 1999;73:160)
• 29 year old pregnant woman (Gynecol Oncol 2002;85:218)
• 31 year old, 35 year old and 63 year old women (Int J Gynecol Cancer 2001;11:316, Gynecol Oncol 2007;107:130, Diagn Pathol 2013;8:122)
• Proximal-type epithelioid sarcoma of the vulva (Int J Gynecol Pathol 2010;29:600)

Treatment
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• Surgical resection with adequate margins and regional (inguinal and pelvic) lymph node biopsy or dissection
• Chemotherapy and radiotherapy

Clinical images
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Vulvar mass

Gross description
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• Single lesion or multiple nodules, with variable satellite-like extensions
• Typically in deep dermis and subcutaneous tissues
• Soft and fleshy to firm, with focal hemorrhage and necrosis

Gross images
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Site unspecified

Micro description
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• Classic features of epithelioid sarcoma (epithelioid and spindled cells in a granulomatous pattern with central hyalinization, necrobiosis or necrosis), are not commonly seen in PES/MRT
• Cells are usually polyhedral and epithelioid with abundant eosinophilic cytoplasm, sometimes with dense accentuation resulting in rhabdoid morphology
• Focal aggregates of plump spindled cells may also be seen
• Nuclei are large, circular or ovoid, with vesicular chromatin and prominent nucleoli
• Pleomorphic cells with multiple nuclei may also be present
• Mitoses are frequent and atypical mitotic figures may be identified
• Individual cell necrosis and geographic necrosis, away from blood vessels, are common features

Micro images
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Core biopsy

H&E, very low power

       

Low power

     

Medium power

   

High power

 

Necrosis

 

Cytokeratin

INI1-BAF47

 

Various images, CK+, vimentin+

 

Perineum

Fig 5: various stains

Cytology description
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• Fine-needle aspiration often yields clusters of cells with similar morphology

Positive stains
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• Vimentin, cytokeratins, EMA (90%)
• p53
• Rhabdoid cytoplasmic inclusions stain variably for cytokeratin and vimentin

Focal positivity
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• Desmin, CD34, CD99, SMA
• CD56, NSE, synaptophysin, ERG

Negative stains
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• INI1 loss is seen frequently
• S100, CD31, MART1

Electron microscopy description
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• EM findings are non-specific, and include abundant cytoplasm with well-developed rough endoplasmic reticulum, increase in free ribosomes, mitochondria, glycogen granules, lysosomes and fat droplets
• Aggregates of intermediate filaments are also seen, corresponding to rhabdoid inclusions
• In other cells, short bundles of intermediate filaments are scattered beneath the plasma membrane or around the nuclei (Pathol Int 2004;54:616, Am J Surg Pathol 1997;21:130)

Molecular / cytogenetics description
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• Alterations in #22q may be present (Genes Chromosomes Cancer 2004;41:283, Pathol Int 2006;56:287)
• SMARCB1/INI1 gene alteration may also be seen (Hum Pathol 2009;40:349)

Differential diagnosis
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• Conventional epithelioid sarcoma
• Epithelioid malignant peripheral nerve sheath tumor
• Epithelioid monophasic synovial sarcoma
• Epithelioid rhabdomyosarcoma
• Extrarenal malignant rhabdoid tumor
• Melanoma
• Mesothelioma
• Undifferentiated carcinoma

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