COX4I1 is a nuclear gene that encodes the common isoform of cytochrome c oxidase (COX) subunit 4 (COX 4-1), which is an integral regulatory part of the mitochondrial respiratory chain (31). COX4 was a biomarker for breast cancer (32) and medullary thyroid cancer (33). The gene discussed is COX4I1; the disease is breast carcinoma.