Furthermore, a higher median TMB is more common in TNBC in comparison to HR+ breast cancer.50,92 Mutations in DNA checkpoint/repair and cell replication pathways have been shown to increase the somatic mutation rate in the tumor and be associated with higher TMB and higher TIL.93 BRCA1 is a key DNA repair gene functioning primarily in homologous DNA repair. The gene discussed is BRCA1; the disease is breast cancer.