Microglandular Adenosis of The Breast

Microglandular adenosis (MGA) is a rare benign condition composed of discrete, glandular structures lined by a single type of epithelial cell; the absence of a myoepithelial mantle makes it unique among benign proliferative lesions of the breast. The haphazardly arranged tubules are characteristically uniform, rounded, open and contain eosinophilic material. The surrounding stroma varies but is frequently hypocellular and collegenous. Immunohistochemical findings are characteristic in that, in addition to positive staining with antibodies to cytokeratin. The epithelial cells stain consistenly for S-100 Protein but are negative for epithelial membrane antigen. Staining with antibodies to basement membrane components and actin confirm the presence of basement membrane and, in all but one study, the absence of a myoepithelial layer it is important that MGA not be mistaken for tubular carcinoma and useful points in the differential diagnosis are highlighted Carcinoma with characteristic features has been reported in association with MGA. The exact relationship between MGA and carcinoma, however, remains uncertain.