MCAT and breast cancer: The similar mutational rate of breast cancer tumors and paired PBs (52.4 vs. 52.3 muts/kb, respectively) observed in our analysis contrasts with previous studies, in which a differential mutational rate between tumor and normal tissue, and a higher frequency of mutations in MT-ATP6, MT-ND3, and MT-CYB genes have been reported [15,16,19,22,28,29,30,31].