Malignant adenomyoepithelioma of the breast with matrix production may be compatible with one variant form of matrix-producing carcinoma: a case report.

We examined a 77-year-old woman who suffered from a left breast tumor. She had undergone right mastectomy for invasive ductal carcinoma at 68 years of age, and rectal resection for mucinous carcinoma at the age of 74 years. The left breast tumor measured 3.8 x 2.5 x 1.6 cm. Neoplastic cells consisted of atypical epithelial and myoepithelial cells. The former cells were polygonal and large. They were located in the periphery of the tumor, arranged in a ductal pattern, and expressed cytokeratins, S-100 protein, maspin, and MIC2. The latter cells were composed of dark cells which proliferated in a periductal pattern, and stellate cells which were located in the center of the tumor. They invaded the chondromyxoid tissues, and proliferated in a lace-like pattern. Atypical myoepithelial cells expressed vimentin, S-100 protein, maspin, and MIC2. We conclude that malignant adenomyoepithelioma of the breast with matrix production might be compatible with a variant form of matrix-producing carcinoma.