Microglandular adenosis (MGA) and atypical microglandular adenosis (AMGA) are extremely rare and unique forms of adenosis of the breast. Both forms of adenosis are strongly associated with carcinoma arising in microglandular adenosis (MGACA) and are recognised as precursor lesions of invasive breast carcinoma. Here we provide a clinical report of a young Taiwanese woman who was diagnosed with MGACA and AMGA by means of echo-guided core biopsy. The subsequent lumpectomy revealed a spectrum of lesions ranging from MGA and AMGA to ductal carcinoma in situ (DCIS) and invasive carcinoma. All of the above lesions have similar immunohistochemical results (expression of S-100 protein, the absence of oestrogen receptors, progesterone receptors and Her2/neu, and the lack of p63 and the smooth muscle myosin-heavy chain) with a rather different Ki-67 labelling proliferation index. This report is of practical interest because the diagnosis of AMGA and MGACA had already been made via needle biopsy.
© 2010 The Authors. Pathology International © 2010 Japanese Society of Pathology and Blackwell Publishing Asia Pty Ltd.