Microglanduar adenosis are strongly S-100 positive, and positive for keratin yet negative for epithelial membrance antigen (EMA). Myoepithelial cells are not seen by hematoxylin and eosin (HE) staining or by immunohistochemistry, which can also lead to a misdiagnosis of invasive carcinoma. However, stains for basement membrane (eg TypeⅣ collagen) are positive around the constituent glands.

图A、B：Microglandular adenosis. A diffusely infiltrative process composed of round glands with a single-cell layer and central lumens with eosinophilic, PAS-positive secretions.

图C: The lesion infiltrates into the surrounding adipose tissue mimicking invasive carcinoma.