Dermatofibrosarcoma protuberans presenting as a subcutaneous mass: a clinicopathological study of 15 cases with exclusive or near-exclusive subcutaneous involvement.

Dermatofibrosarcoma protuberans (DFSP), a cutaneous fibrohistiocytic tumor of intermediate (borderline) malignancy, typically arises in the dermis and subsequently infiltrates the subcutaneous tissue. Very rarely DFSP may either arise within the subcutaneous fat without dermal involvement or show very extensive subcutaneous involvement with only minimal and clinically subtle dermal involvement. We present the clinicopathological features of 15 cases of DFSP showing exclusive or near-exclusive involvement of the subcutaneous fat. The differential diagnosis with other subcutaneous spindle cell neoplasms is emphasized. Awareness of this rare subset of DFSP should prevent its misdiagnosis as other less aggressive tumor types.