Malignant adenomyoepithelioma of the breast combined with invasive lobular carcinoma

Presented herein is the first case of malignant adenomyoepithelioma (malignant AME) of the breast combined with invasive lobular carcinoma (ILC) in a 53‐year‐old woman. Histologically, the tumor was composed of nodular proliferation of biphasic epithelial and myoepithelial carcinoma, partially surrounded by ILC. Interestingly, ILC metastasized to the axillary lymph nodes, while biphasic epithelial and myoepithelial carcinoma hematogenously metastasized to the lung and the kidney. On immunohistochemistry the biphasic carcinoma consisted of cytokeratin (CK) 8/18‐positive/CK5/6‐positive/smooth muscle actin (SMA)‐negative inner carcinoma cells and CK8/18‐positive/CK5/6‐positive/SMA‐positive outer carcinoma cells. The monophasic ILC cells had a CK8/18‐positive/CK5/6‐negative/SMA‐negative staining pattern. Although it is unclear whether both ILC and biphasic epithelial and myoepithelial carcinoma originated from AME or whether ILC occurred independently of malignant AME, this is an exceptionally rare case, which might give rise to a special consideration of the histogenesis of breast cancer.