TP53 and ductal breast carcinoma in situ: Importantly, a recent genomic study of human High-Grade Ductal Carcinoma In Situ (DCIS), which is believed to be a precursor lesion of invasive ductal carcinoma, revealed that the p53 pathway was deactivated in all DCIS samples analysed, regardless of TP53 mutation status or intrinsic subtypes12.