BRCA1 protein localization in frozen and FFPE sections of poorly differentiated adenocarcinoma (PDA) from patient no. 22 using avidin-biotin-detection system. A. H&E stained frozen section of tumor. B. Consecutive section of the tumor stained with mouse monoclonal AP16 antibody and biotinylated anti- mouse IgG showed that few of the cells showed distinct, punctate nuclear staining (2), and insert shows focal staining. C. Standard dilution of mouse IgG served as negative control. D. H&E section of FFPE tissue from patient no.22. E. Consecutive section of the same tumor treated with pressure cooker antigen retrieval and stained with the MS110 antibody showed that few of the cells exhibited distinct nuclear staining (2) and insert shows darkly stained and unstained nuclei. F. Consecutive control section of FFPE tissue without primary antibody. (×200) insert (×2000).