Interobserver Variability in HER-2 Immunostaining Interpretation of Metastatic HER2 Low Breast Cancers in Cytology Specimens.

This study highlights the interobserver variability of HER-2 immunostain interpretation for HER-2 low category of breast carcinomas. We recommend the need for more robust laboratory techniques including molecular for uniform identification of these unique targetable metastatic breast carcinoma groups.