Microglandular adenosis, apocrine adenosis, and tubular carcinoma of the breast. An immunohistochemical comparison.

Four cases of microglandular adenosis (MA), together with four cases of apocrine adenosis (AA) and 10 cases of tubular carcinoma (TC) of the breast were studied at the light and immunohistochemical level. One case of MA was studied with electron microscopy. MA is characterized by an absence of myoepithelial cells (ME), epithelial membrane antigen (EMA), and gross cystic disease fluid protein (GCDFP-15). The absence of EMA in MA makes it unique among benign glandular hyperplasias of the breast. AA contains myoepithelial cells and a distinct basal lamina. It is characterized by the presence of GCDFP-15, the specific apocrine marker, which is not present in MA. TC lacks both myoepithelial cells and a basal lamina. It is negative for GCDFP-15. Periductal and vascular elastosis are common and usually prominent, whereas they are not found in either MA and AA. Other stromal changes further distinguish the three lesions. These three distinct entities can be separated objectively and unequivocally and it is essential that this be done so as to prevent confusion.