Pleomorphic adenoma of the breast: a report of two cases and a literature review

Pleomorphic adenoma of the breast (PAB) is an extremely rare tumor in the breast. Herein, we reported two Asian female patients diagnosed as PAB and reviewed the relevant literature briefly. The two cases were both diagnosed as fibroadenoma in breast ultrasonography before surgery. Case one is a 28-year-old woman presented with a seven year history of a slowly-growing painless mass in left breast, which was about 1.46×0.93 cm in size. Case two is a 47-year-old female who had a complaint of left breast mass three months ago, which was 2.31×1.37 cm in size. The two tumors both located under areola. The two patients both underwent lumpectomy. Microscopically, they were both comprised of mixture of epithelial cells and myoepithelial cells embedded in myxochondroid matrix background. Immunohistochemically, the two cases displayed positive cytokeratin 7 (CK7) for epithelial cells, positive smooth muscle actin (SMA) and S-100 for myoepithelial cells. PAS staining was positive in case two. According to the pathologic histology and immunohistochemical findings, the two cases were diagnosed as PAB. However, the pathogenesis of PAB has been unclear and further studies remain to be researched.