BRCA1 protein in frozen and FFPE sections from lactating tissue from patient no.4 with a BRCA2 mutation. A. H&E stained frozen section of lactating tissue. B. Consecutive section of the same tissue stained with the mouse monoclonal AP16 antibody and the avidin-biotin peroxidase detection system showed that many of the lactating cells showed punctate nuclear granules. C. Negative control section using standard dilutions of mouse IgG. D. H&E section of FFPE lactating tissue. E. Consecutive section of the same tissue treated with pressure cooker antigen retrieval and stained with the MS110 antibody showed that most of the lactating cells exhibited moderate homogeneous nuclear staining (3). F. Consecutive control section of FFPE tissue without primary antibody. (×200).