ARID1A and ductal breast carcinoma in situ: DCIS and IDC‐NST shared 29 synonymous and nonsynonymous mutations not seen in JP, including a truncating mutation in the chromatin remodeling gene ARID1A, missense mutations in KMT2C and PIK3CB, and an E14K hotspot mutation affecting NUP93, a nucleoporin implicated in cell migration [29] (Figure 3B,C).