In addition, this patient group harbored pathogenic germline variants in other genes previously known or suggested to be associated with breast cancer to a varying extent, including ATR, CDH1, CHEK1, CHEK2, ERCC2, FAN1, SEC23B, and SMAD9. However, with the exception of a single patient carrying the moderately penetrant CHEK2 variant, c.1100del, p.Thr367Metfs*15, none of these variants had indications of LOH in the breast tumor samples. This evidence concerns the gene SMAD9 and breast cancer.