To address this question, this study sequenced all exons and exon-intron boundaries of NTHL1 in 9,771 subjects in the hereditary BrEAst Case CONtrol (BEACCON) study, comprising index cases from hereditary breast cancer families who tested negative for germline pathogenic variants in BRCA1 and BRCA2 and cancer-free older female controls (average 49.7 years vs. 65.6 years) in the same population. Here, NTHL1 is linked to breast cancer.