Mesenchymal and Fibroepithelial Tumors of the Breast

Benign mesenchymal tumors that occur elsewhere in the body have been described in the breast, including lipoma, angiolipoma, leiomyoma, neurofibroma and schwannoma. Malignant mesenchymal tumors of the breast other than angiosarcomas are extremely rare. However, any type of sarcoma may occur in the breast as a primary lesion, including liposarcoma, leiomyosarcoma, rhabdomyosarcoma, malignant peripheral nerve sheath tumor, and osteosarcoma. Fibroepithelial tumors are biphasic neoplasms characterized by the proliferation of both epithelial and mesenchymal elements. Fibroadenoma and phyllodes tumors constitute the major entities.