TIAM1 and ductal breast carcinoma in situ: TP53 mutation‐associated ESR1 overexpression was involved in the transition from DH to DCIS, 6q21 amplification‐associated NR3C1 overexpression helped DCIS_Pure (pure DCIS, no histologic evidence of invasion) cells avoid immune destruction, the TIAM1‐AR‐AKR1C1 axis promoted cell invasion and migration in DCIS_adjIDC (DCIS regions of invasive cancers) (Figure S8C, Supporting Information).