Aims: Epithelioid sarcoma (ES) is a distinct sarcoma-type with a specific morphology and immunophenotype. Whereas focal myxoid change does occur, to our knowledge only two cases of ES with diffuse myxoid stroma have been reported previously. To characterize more clearly the myxoid variant of ES, we describe six additional cases and discuss the differential diagnoses.
Methods and results: Cases were retrieved from the authors' files and studied histologically, immunohistochemically and by molecular methods. The age of the patients, four females and two males, ranged from 16 to 74 years (median: 33 years). The neoplasms arose in an extremity (two cases), the abdominal wall, groin, perineum and shoulder (one case each). Histologically, four cases were of the conventional type, and two were of the proximal type and the immunophenotype was typical for ES. The tumour stroma, however, revealed prominent myxoid changes, ranging from 50 to 90% (median: 75%). Only one of the proximal type ES showed a SMARCB1 mutation, whereas the other tumours showed no mutation.
Conclusions: The myxoid variant of ES represents a diagnostic challenge and may be confused with other benign and malignant myxoid neoplasms. The main differential diagnosis is myoepithelioma of the skin and soft tissue.
© 2010 Blackwell Publishing Limited.