PRDM9 and head and neck squamous cell carcinoma: Noteworthy, our pan-cancer mutation analysis recognized PRDM9 as one of the most mutated genes of the PRDM family with frequencies ranging from 0.5% to 15.4% and higher than 5% in multiple cancers, such as DLBCL, HNSCC, endometrial, esophageal, stomach, and colon carcinomas, kidney and lung tumors, and melanoma [45].