BRCA1 protein in frozen and FFPE sections of moderately differentiated adenocarcinoma (MDA) from patient no. 2. A. H&E stained frozen section of the tumor. B. Consecutive section of the same tumor stained with the mouse monoclonal AP16 antibody and the avidin-biotin peroxidase detection system showed that many of the cells exhibited multifocal dot-like nuclear staining of category (2); insert shows subnuclear foci. C. Negative control section using standard dilutions of mouse IgG showed essentially no staining. D. H&E section of FFPE tissue from patient no. 2. E. Consecutive section of the same tumor treated with pressure cooker antigen retrieval and stained with the MS110 antibody showed that most of the cells exhibited moderate nuclear staining of category (3); insert shows dark staining. F. Consecutive control section of FFPE tissue without primary antibody. (×200) inserts (×2000).