Mammary myofibrosarcoma: case report and literature review.

A case of myofibrosarcoma of breast is reported. A female patient aged 81 years presented with a mammary mass lesion. Histologically, the tumor consisted of neoplastic spindle cells arranged in fascicles and with variably cellularity and hyalinization. Immunohistochemical studies showed expression of vimentin, smooth-muscle actin, and Bcl-2, but not desmin, S-100, C-kit, or CD34. Proliferative index identified by Ki67 was approximately 30%. Electron microscopy revealed variable amount of rough endoplasmic reticulum, myofilaments, fibronexus junctions, and fibronectin fibrils. The histological, immunohistochemical, and ultrastructural features of this tumor were consistent with myofibrosarcoma. This case will be one of the very few cases of ultrastructurally confirmed mammary myofibrosarcoma reported in the literature and contributes to the recognition of this rare mammary malignant neoplasm. The literature on mammary myofibrosarcoma and its differential diagnosis is also reviewed.