Malignant fibrohistiocytoma (MFH) of the breast. Primary and postirradiation variants - an ultrastructural study.

Two cases of malignant fibrohistiocytoma (MFH) of the mammary gland are presented. Patient No. 1 had been previously locally irradiated for an infiltrating duct carcinoma (5600 rads) 5 years earlier. Prognosis of postirradiation MFH was poor and the patient died within the first year after diagnosis of the second malignancy. The primary MFH (Case No. 2) is free of disease after a 5-year follow-up period, having been submitted to a radical mastectomy. Histological appearance is in accordance with previously published cases. No marked differences existed between both cases at optical level. Lysozyme (PAP technique) was observed within isolated histiocytes. Electron microscopy distinguished up to 4 different cell types within the neoplasm: fibroblasts, histiocytes, mixed cells of fibro-histiocytic appearance, and more immature blastemal cells. Transitional forms existed among them.