The pan-cancer expression of LDHC/LDH-C4 has been assessed, and the results of IHC based on high-throughput tissue microarray analyses suggest the highest positivity rate of LDH-C4 in LUAD (96.7%) (63), followed by breast cancer (BC) (91.55%) (36), and hepatocellular carcinoma (HCC) (55.84%) (37). The gene discussed is C4A; the disease is breast cancer.