Dermatofibrosarcoma protuberans is a slow-growing, local aggressive fibrous tumor of the subcutaneous tissue, frequently seen in the proximal extremities and the trunk. Its occurrence in the breast is very rare. Herein, we present a female who presented with a breast mass, and aim to discuss pathological features and differential diagnosis of dermatofibrosarcoma protuberans. A 44-year-old female presented to our clinic with a mass on her breast. Physical examination revealed a 8x5.5 cm mass with multilobular nodules on the skin in the lower inner quadrant of her right breast. Her mammography revealed a hyperdense, 7.5x6.5 cm, well-demarcated, lobulated mass in the right breast, which caused nodules on the lower paraareolar portion of the breast skin. There was no axillary lymphadenopathy on both clinical and radiologic examinations. A core needle biopsy had been performed prior to her referral to our center, which revealed a ‘spindle cell lesion’. The patient underwent simple mastectomy. On macroscopic examination; the skin over the lesion appeared ulcerated, and there was a well-defined solid mass, which was pale white-tan on the cut surface. Microscopic examination revealed monotonous spindle cell proliferation arranged in storiform pattern within the collagenous stroma with irregular extensions into deep adipose tissue. There were no necrosis or nuclear pleomorphism. The mitotic rate was 2-3/10 HPF. Immunohistochemically tumor cells showed diffuse CD34 positivity, and S100, EMA and SMA negativity. Based on histopathological and immunohistochemical findings, the lesion was diagnosed as dermatofibrosarcoma protuberans. Local recurrence is expected in 20-50% of these cases. Its treatment requires complete surgical excision with wide margins. Distant metastases, although rare, have been reported.

Keywords: Dermatofibrosarcoma, skin neoplasm, breast, diagnosis, differential