BRCA1 and neoplasm: When compared with tumors from the KP model, tumors from the KB1P model exhibit a high degree of genomic instability with many chromosomal gains and losses, due to the loss of Brca1. KB1P and KP mice exhibit an ~ 200‐day difference in tumor‐free survival and overall survival, with KB1P mice succumbing earlier to tumor development (Liu et al., 2007).