Breast carcinoma with features of osteosarcoma--a light and electron microscopic and immunohistochemical study

Reported is the case history of a 58-year-old woman with a lump in the left breast. The tumor was composed of two nodules, sharing a common portion. Grossly, one was an irregular hard tumor that was grayish in color, and the other was a well circumscribed cystic tumor that showed necrosis and a hemorrhage that had filled it with a reddish soft mass. Light microscopically, combined features of a scirrhous carcinoma and of an osteosarcoma were observed in each nodule, but the common portion was consistent with a metaplastic carcinoma, with cancer cells and sarcoma-like cells closely mingled. An ultrastructural study showed that the sarcoma-like cells were composed of polymorphic cells that resembled osteoblasts, myofibroblasts, osteoclasts, histiocytes, and undifferentiated tumor cells. Immunohistochemically, vimentin and alpha 1-antitrypsin in the sarcoma-like cells were positive, suggesting these cells were of a mesenchymal rather than of an epithelial origin.