It should be noted that no significant differences in the number of somatic mutations were found between the four PALB2-associated breast cancers analyzed by WES lacking bi-allelic PALB2 inactivation (one ER−/HER2− and three ER+; median 103, range 59–109) and the 683 ER−/HER2− and ER+ non-BRCA1/2/PALB2-associated breast cancers (median 51, range 2–6666; P > 0.05, Mann–Whitney U test and bootstrapping-corrected). This evidence concerns the gene ESR1 and breast cancer.