Cystosarcoma phyllodes of the breast with features of malignant fibrous histiocytoma.

A case of a 33-year-old female with metastasizing malignant cystosarcoma phyllodes of the left breast showing histologic features of malignant fibrous histiocytoma is reported. Metastases consisting of only undifferentiated mesenchymal cells were found in the lungs, liver, pleurae, kidneys, ileum, and vertebrae. Seven cases of fibrohistiocytic tumors of the breast previously recorded in the literature were reviewed. Although rare, this type of tumor should be included in the differential diagnosis of mesenchymal mammary tumors.