TP53 and ductal breast carcinoma in situ: We found that TP53 mutation was high‐frequency event of BRDC, and occurred as early as in the tumorigenesis stage with a frequency of 50% in DCIS, whereas no TP53 mutation was observed in DH (DCIS versus DH, Fisher's exact test, p < 0.0001) (Figures1C and 2A).