BRCA1 and cancer: Using MiMouse, we profiled >250 tumors from high-grade serous carcinoma GEMMs based on conditional inactivation of Brca1 (B), Trp53 (P), Pten (Pt), Rb1 (R), and/or Nf1 (N) and a colorectal carcinoma GEMM based on conditional inactivation of Apc, Kras, and/or P. We confirmed increased genomic instability in high-grade serous carcinoma tumors, with BPPt cancers having both the shortest latency and the least genomic instability.