To further study the heterogeneity of BRCA1-deficient mammary tumors, we collected 23 tumors from two previously established mouse models, where MMTV-Cre driven loss of BRCA1 (MMTV-Cre; Brca1fl/fl) specifically develops mammary tumors (BrTs) in 1-1.5 year, while combination of Trp53 mutation (MMTV-Cre; Brca1fl/fl;Trp53fl/+) could greatly accelerate the tumorigenesis (Figure 1A). The gene discussed is BRCA1; the disease is breast cancer.