Upon restriction of the comparison to the 18 ER+ /HER2− PALB2-associated breast cancers and the 441 ER+/HER2− non-BRCA1/2/PALB2-associated breast cancers, PALB2, NOTCH3, ARID1A, DNMT3A, BRIP1, FGFR4, CD79A, and GNAQ (all P < 0.05; Fisher’s exact test) were significantly more frequently mutated in the PALB2-associated breast cancers (Fig. 4b), but similarly only PALB2 and NOTCH3 remained significantly different after bootstrapping resampling (P < 0.01, Fisher’s exact test and bootstrapping-corrected; Supplementary Table 5). This evidence concerns the gene ESR1 and breast cancer.