Multiple Histological Subtypes of Dermatofibrosarcoma Protuberans Occurring in the Same Tumor.

Dermatofibrosarcoma protuberans (DFSP) represents a low-grade cutaneous sarcoma which may have different histological aspects, presenting as a fibrosarcomatous, pigmented, juvenile, myxoid, atrophic, sclerosing or myoid lesion. Some of these subtypes may occur isolated or in association with one of the others creating hybrid lesions. We present the case of a 66 years old woman having a 4 cm diameter tumor located on the abdominal wall. Histopathological examination of the resection specimen revealed areas of typical DFSP associated with fibrosarcomatous transformation, myoid and myxoid areas. Also, focally, pleomorphic tumor cells and foreign-body type multinucleated giant cells were observed. Immunostains revealed CD34 positivity in typical DFSP and myxoid areas with negative staining of some of the tumor cells in fibrosarcomatous areas and negative staining of myoid areas. Smooth muscle actin was positive in myoid areas. The nature of myoid fascicles in DFSP is a matter of debate, being uncertain whether these represent a type of tumor differentiation or a reactive myoid proliferation. In this particular case, finding the association of myoid cells with blood vessel walls sustains their reactive nature. We present the morphological aspects of the different areas of the tumor with emphasis on differential diagnostic problems and clinical implications.