BRCA1 and breast cancer: To further illustrate, studies have found approximately 70% of BRCA1-mutated breast cancer to exhibit a basal-like pattern in molecular subtype compared to 20% in BRCA1-wild-type breast cancer; 57–68% of BRCA1-mutated breast cancer exhibit triple-negative breast cancer (TNBC) in surrogate subtype compared to 13% in BRCA1-wild-type breast cancer, and a 50–79% response to PARPi compared to 10–33% in BRCA1-wild-type cases [14,15,16,17,18].