Adenoid cystic carcinoma arising in an adenomyoepithelioma of the breast.

Adenomyoepithelioma is a mixed epithelial and myoepithelial tumour. In rare cases adenomyoepitheliomas give rise to carcinomas with epithelial, myoepithelial, or mixed epithelial and myoepithelial differentiation. Carcinomas arising in adenomyoepithelioma range from low grade to high grade, and 15 cases have been reported in the literature. We describe a 36-year-old woman with a very rare adenoid cystic carcinoma arising in a tubular adenomyoepithelioma. The histogenesis of carcinoma arising in an adenomyoepithelioma is discussed.