On an individual gene level, we observed >5-fold enrichment for mutations in CHEK2 (29 of 3382 versus 0 of 640, P = 0.001 after adjustment for multiple comparisons) in ER+/HER2− breast cancer samples relative to TNBCs, but no statistically significant enrichment for ATM, ATR, or CHEK1 mutations in either subtype (Fig. 1B). This evidence concerns the gene ESR1 and breast carcinoma.