ESR1 and breast cancer: As an exploratory, hypothesis-generating analysis we investigated whether PALB2-associated breast cancers would differ from non-BRCA1/2/PALB2-associated breast cancers from TCGA.19 Given that none of the PALB2-associated breast cancers included here was of ER-/HER2+ phenotype, ER-/HER2+ non-BRCA1/2/PALB2-associated breast cancers from TCGA were excluded, and the remaining 683 ER−/HER2− and ER+ (including ER+/HER2+and ER+/HER2−) breast cancers were employed for the analyses.