237 A Case of Dermatofibrosarcoma Protuberans of the Breast

Abstract

A 62-year-old woman underwent routine mammography as part of her annual health check. The mammography showed a 5.7 cm irregular mass in the left breast, posterior to the nipple and in the middle depth. A needle core biopsy was performed and sent to pathology department for evaluation. Histopathologic examination revealed the core biopsy to be involved completely by a monomorphic cellular proliferation of spindle-shaped cells, arranged in bundles displaying storiform and herring bone growth patterns. The lesion also showed frequent mitosis. The differential diagnosis for this spindle cell breast tumor included myofibroblastoma, metaplastic carcinoma, primary breast sarcoma, malignant phyllodes tumor, and dermatofibrosarcoma protuberans (DFSP). Based on the differential diagnosis an immunohistochemical panel composed of CD34, AE1/AE3, actin, desmin, S100, CK903, CD117, CD10, CD99 and FLI-1 was performed. The cells showed diffuse positivity for CD34 while all other stains were diffusely negative. A Ki67 immunostain was performed, which showed >20% positivity. The results of the immunohistochemical panel combined with clinical and morphologic features led to a diagnosis of dermatofibrosarcoma protuberans of the breast. DFSP is a rare cutaneous low-grade sarcoma that arises from the dermis and usually involves the trunk. The involvement of the breast by DFSP is extremely rare and can be a diagnostic challenge for the pathologists. A combination of immunohistochemistry and morphology can usually aid the diagnosis as in our case.