C4A and breast cancer: LDH-C4 has been detected by IHC in CRC, BC, prostate cancer (PC), LUCA, and RCC with corresponding positivity rates of 50.00%, 22.22%, 25.00%, 25.00%, and 90.91% (Figure 2D), respectively, in the Human Protein Atlas (HPA) database (https://www.proteinatlas.org/about/licence).