Adenomyoepithelioma of the breast is a rare tumor. A myoepithelial carcinoma arising within an adenomyoepithelioma is even more unusual. There are a limited number of reports discussing myoepithelial carcinoma; most of them describe pathological findings, but not imaging findings. We present a case of a 55-year-old woman who had a screen-detected myoepithelial carcinoma arising within an adenomyoepithelioma in her right breast. Upon the completion of a mammography and sonography an oval shaped mass with an indistinct margin in the upper portion of the right breast had been seen. It as appeared to be a spiculated, irregular-shaped, peripheral-enhancing mass on an MRI. On sonography-guided biopsy, an epithelial-myothelial tumor was confirmed, and the possibility of myoepithelial carcinoma was suggested. Breast-conserving surgery with a sentinel lymph node dissection was performed, and a pathological examination revealed a myoepithelial carcinoma arising within an adenomyoepithelioma.
