[Dermatofibrosarcoma protuberans of the breast: a case report]

We describe a dermatofibrosarcoma protuberans (DFSP) of the breast and briefly report about such cases previously mentioned in the literature. A 27-year-old woman was referred because of the progressive increase, during pregnancy, of a mammary nodule located between the internal quadrants of the right breast. Its clinical and radiologic features suggested a fibroadenoma. Lumpectomy revealed a 3-cm, gray-whitish, fasciculated nodule. Histological examination showed a neoplasm characterized by a highly and monomorphic cellular proliferation of spindle-shaped cells, arranged in bundles displaying repetitive storiform growth pattern and infiltrating the adjacent mammary tissue. Lack of necrosis and low mitotic rate was observed. At immunohistochemistry the tumor cells were diffusely positive for vimentin and CD34, but negatively stained with CD99, bc-2, desmin, smooth-muscle actin, S100 protein and cytokeratins. A diagnosis of mammary dermatofibrosarcoma protuberans (DF-SP) was posed. Neoplastic involvement of surgical margins led to a subsequent quadrantectomy without regional lymphadenectomy. The patient was alive and disease-free at the 8-month follow-up. Mammary DFSP is rare. Its preoperative diagnosis is extremely difficult, particularly when radiologic images show an intraparenchymal lesion with round borders. We report such a case and briefly review the pertinent literature. Morphologic parameters to distinguish DFSP from other spindle cell lesions of the breast are discussed.