CD274 and cancer: Many studies have shown that PD-L1 expresses in HPV-related lesions including cutaneous warts [7], HISIL and cancer cells of the cervix, as well as in head and neck carcinomas [41–43], and the overexpression of PD-L1 in keratinocytes can protect HPV infected cells from host immune destruction, which has been regarded as a mechanism of HPV immune evasion rather than a result of malignancy.