Primary cutaneous malignant granular cell tumor: an immunohistochemical study and review of the literature.

Granular cell tumors (GCTs) are uncommon soft tissue tumors characterized by cytoplasmic granular appearance of the neoplastic cells. Malignant granular cell tumors (MGCTs) comprise less than 2% of GCTs and are mostly found in the subcutaneous soft tissues of the lower extremities, especially the thighs. Very few cases have been reported in the skin. The uncommon occurrence of cutaneous MGCTs and their histopathologic similarities with their benign counterpart make difficult the diagnosis of this particular malignancy. We describe a primary cutaneous MGCT that presented as a left posterior chest wall mass in a 51-year-old woman. Local excision was performed for the primary tumor, which was first interpreted as an atypical GCT, but 3 months later a left axillary mass appeared, and subsequent axillary lymph node dissection demonstrated metastatic disease in 4 of 12 excised lymph nodes. We report the immunophenotype of this primary cutaneous MGCT, which was studied with an ample panel of antibodies and compare our results with those of the few previously reported cases in the skin and subcutaneous soft tissues.