[Clinicopathologic features of mammary microglandular adenosis with carcinoma: a study of 5 cases]

Objective: To study the clinicopathologic, immunohistochemical features, differential diagnoses and prognosis of mammary microglandular adenosis with carcinoma (MGACA) with micropapillary pattern. Methods: Five cases of MGACA were collected from 2010 to 2016 and reviewed for their clinical, histologic features and outcome.EnVision method were done for S-100 protein, cytokeratin (CK), p63, Calponin, smooth muscle myosin heavy chain (SMMHC), PR, ER and HER2. Results: Histologically, microglandular adenosis(MGA), atypical MGA (AMGA) and invasive carcinoma were seen in all five cases of MGACA. The invasive component was metaplastic carcinoma in one case and ductal in four cases. All epithelial cells were S-100 and CK positive in MGA, AMGA and invasive carcinoma. p63, Calponin and SMMHC negativity confirmed the lack of a myoepithelial cell layer in MGA, AMGA and MGACA. PR was weakly focally positive in one case, but ER and HER2 were negative in all cases (four cases were triple negative). Ki-67 index was 20% to 40%. Laminin and collagen Ⅳ staining showed the presence of basement membrane in MGA and AMGA, except MGACA. The follow-up time ranged from 3 months to 6 years, and all patients were alive without recurrence or distant metastasis. Conclusions: MGACA is a rare tumor with distinct morphological and IHC features. Compared to most triple-negative breast cancers, MGACA seems to have a relatively favorable outcome.