Invasive breast carcinoma arising in microglandular adenosis: a case report and review of the literature.

Microglandular adenosis of the breast is an extremely rare, benign lesion. Carcinoma arising in microglandular adenosis has been reported in up to 27% of patients with microglandular adenosis. We reported a case of invasive carcinoma arising in microglandular adenosis. A lumpectomy was performed on a 42-year-old female because of a mass in the right breast. Grossly, the lesion was ill-defined with thickened areas. Histologically, this case was consistent with carcinoma arising in microglandular adenosis and showed clear transition from microglandular adenosis through atypical microglandular adenosis to in situ and invasive carcinoma. All the epithelial cells were positive for cytokeratin7, S-100 protein, but negative for estrogen receptor, progesterone receptor, and Her2/Neu. No myoepithelial cells were demonstrable with immunohistochemical staining for smooth muscle actin, muscle-specific antigen or P63. Periodic acid-Schiff staining showed the presence of a basement membrane in microglandular adenosis, atypical microglandular adenosis, in situ carcinoma and the absence in invasive carcinoma. To the best of our knowledge, this is the first reported case of carcinoma arising in microglandular adenosis in China.