In addition, the Breast Cancer 1-2 (BRCA1/2) genes are main regulators of a cellular DNA damage repair system (homologous recombination repair, HRR); the failure of HRR is due to combined germline and somatic mutations of BRCA1/2 and/or other genes, favoring the activation of alternative and less effective DNA repair pathways (such as base/nucleotide excision repair or mismatch repair system) [7,8,9,19,23,53,56,92,163,164]. The gene discussed is BRCA1; the disease is breast cancer.