Malignant granular cell tumor with unusual histological features.

Malignant granular cell tumor, although uncommon, should be differentiated from a number of granular cell-containing tumors. Reported herein is a distinctive variant of malignant granular cell tumor, clinically presenting as a rapidly enlarging scrotal mass, in which some areas morphologically displayed features indistinguishable from Kaposi sarcoma. Cells in areas simulating Kaposi sarcoma were immunohistochemically the same as typical granular cells in other portions of the tumor. The recognition of this pattern is important because it may predominate and overshadow the original nature of tumor.