Case of the Month

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 Do you think you have a good case of the month? Email it to edit@thepathologist.com

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Answer to last month’s Case of the Month… E. Mammary analog secretory carcinoma (MASC) This salivary gland tumor is composed of a single cell population of cells arranged into cribriform and microcystic glands, focally containing secretory material in their lumina. Tumor cells have uniform vesicular nuclei with visible nucleoli and a well-developed eosinophilic vacuolated cytoplasm. There are no mitotic figures and there is no necrosis. Overall the tumor appears histologically as a low-grade malignancy resembling secretory carcinoma of the breast (1). Reference A Skálová et al., Am J Surg Pathol, 34, 599–608 (2010).

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