Zhou S, Yang F, Bai Q, et al. - This study was conducted to assess whether intense basolateral membrane staining indicates HER2 positivity in invasive micropapillary breast carcinoma. They recruited a total of 147 cases of invasive micropapillary carcinoma with moderate-to-intense HER2 immunostaining. In this study, 117 of the tumors (80%, 117/147) had moderate staining, and 38 (32%, 38/117) displayed HER2 gene amplification by fluorescence in-situ hybridization. Furthermore, HER2 gene was elaborated in all the remaining 30 tumors (20%, 30/147) that exhibited intense basolateral membrane staining. Despite if the staining is incomplete, invasive micropapillary carcinoma with intense clear linear basolateral membrane immunostaining shows HER2 positivity. They should be labeled as immunohistochemical 3+ rather than immunohistochemical 2+, which would avoid further fluorescence in-situ hybridization-testing method and greatly save the related time, labor, and financial costs. Presently, ensure all individuals with HER2 gene addition obtain effective targeted therapy in time.