ARID1A and breast cancer: Of the 410 cancer genes included in MSK-IMPACT, recurrently mutated genes found in the 24 PALB2-associated breast cancers included PIK3CA (n = 7, 29%), PALB2 (n = 5, 21%), TP53 (n = 5, 21%), NOTCH3 (n = 4, 17%), KMT2A (n = 3, 17%) and ARID1A (n = 3, 17%; Fig. 1, Supplementary Table 3).