Epithelioid Sarcoma
Definition
- Keratin positive soft tissue tumor composed of large epithelioid cells almost always involving distal extremities (see also proximal type epithelioid sarcoma)
Alternate/Historical Names
- Classical type epithelioid sarcoma
- Large cell epithelioid sarcoma
Diagnostic Criteria
- 95% keratin positive
- CD34 50%
- Almost always involves distal extremities of young adults and children
- Poorly circumscribed, often multinodular
- Separate and fused nodules and sheets of cells
- Frequent central necrosis
- May appear histologically as necrotic granulomas
- Brightly eosinophilic collagen in and around nodules
- Medium to large epithelioid and spindled cells
- Rarely predominantly spindled
- Abundant brightly eosinophilic cytoplasm
- Frequently with sharp cell borders
- Nuclei may be eccentric
- Moderate nuclear pleomorphism
- Mitotic figures infrequent to numerous
- Occasional features
- Perineural invasion
- Vascular invasion
- Myxoid areas or extensive hyalinization
- Calcification or ossification
- Hemorrhage
- Cyst formation
- Small cell pattern with scant cytoplasm
- Fibroma-like variant
- Pure spindled cells
- Other than the name, classical type epithelioid sarcoma shares only the distinctive immunophenotype of proximal type epithelioid sarcoma.
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting:: July 27, 2007
Latest update: December 12, 2008