ESR1 and breast cancer: As expected, the 12 PALB2-associated breast cancers with bi-allelic PALB2 inactivation analyzed by WES (ten ER+/HER2− and two ER−/HER2−) harbored a significantly higher number of somatic mutations (median 139.5, range 63–269) than the 568 ER+/HER2− and ER−/HER2− (median somatic mutations 50, range 2–6666; P = 0.0001, Mann–Whitney U test; P = 0.005, bootstrapping-corrected).