Desmoplastic primitive nonneural granular cell tumor of the skin.

Primitive nonneural granular cell tumor of the skin was first described by LeBoit et al in 1991 as "primitive polypoid granular cell tumor." Few cases have been reported to date, all being polypoid or deep well-delimited lesions and formed by large spindle or polygonal granular cells with moderate nuclear atypia and increased mitotic activity. This granular cell population does not have a Schwannian, myogenic, melanocytic, fibroblastic, histiocytic, or epithelial differentiation. We report a case that fully satisfies the criteria for primitive nonneural granular cell tumor of the skin and, in addition, shows an extensive desmoplastic stroma. This desmoplastic variant of primitive nonneural granular cell tumor, which to our knowledge has not been previously reported, should be recognized to appropriately face the differential diagnosis with the malignant granular cell tumor, whose criteria for malignancy cannot be applied to primitive granular cell tumors.