To further understand how tumors evolve from premalignant mammary glands to PTs and metastases due to copy number changes upon the loss of Brca1, we analyzed all cells based on the tumor developmental stages in mice in the following order: VWMG, VMMG, 476WMG, 476MMG, 476PT, 153PT, and 153LMT (Fig. 5a; Supplementary Data 3). Here, BRCA1 is linked to neoplasm.