Immunohistochemistry: Mammary analogue secretory carcinomas (MASC) are usually positive for cytokeratin AE1/AE3, CAM5.2, Cytokeratin 7, vimentin, STAT5a and S-100 protein. Mammaglobin and GCDFP-15 are also positive. DOG-1 is negative. Basal cell and myoepithelial cell markers, including CK5/6, SMA, p63, and calponin are usually not expressed. This focus shows an admixture of papillary, solid, and cribriform architecture.