A 52-year-old woman was admitted with a palpable mass on the abdominal wall. This tumor had developed at the same site of a previously resected dermatofibrosarcoma protuberans. The biopsy specimen from the recurrent tumor revealed malignant fibrous histiocytoma. Immunohistochemistry with anti-CD34 antibody revealed diffuse linear positivity on the tumor cells of dermatofibrosarcoma protuberans and negativity on malignant fibrous histiocytoma. Anti CD34 antibody was valuable for a differential diagnosis of these two lesions.