Soft tissue tumor

The tumor shown here was resected from the soft tissue of the axilla of a 26-year-old man. The immunohistochemical stains gave the following results: positive for smooth muscle actin (a), and focally positive for microphthalmia transcription factor (b), Melan A; negative for S-100, pancytokeratin and desmin. What is the most likely diagnosis?

Credit: Wei Cui, University of Kansas Hospital

a.

b.

A Metastatic melanoma

B Clear cell sarcoma of soft tissue

C Malignant perivascular epithelioid cell tumor (PEComa)

D Leiomyosarcoma

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