BRCA1 and ovarian cancer: In Japan, the proportion of germline variants in ovarian cancer is approximately 18%, and the major genes are BRCA1, BRCA2, mismatch repair genes [MutL protein homolog (MLH) 1, MLH2, MLH6, and postmeiotic segregation increased 2], RAD51 Paralog D, and ataxia telangiectasia mutated (ATM) (26).