However, it is not without limitations, including the subjectivity and adherence to test interpretation criteria, the use of multiple PD-L1 clones (22C3, SP142, SP263, 28.8), the existence of several protocols for the interpretation of the test (TPS, IC, CPS), and the standardization of cut-off points only for some solid tumors such as triple-negative breast cancer, NSCLC, cervical carcinoma, squamous cell carcinoma of the head and neck, and gastroesophageal junction carcinoma [41,42,43,44]. Here, CD274 is linked to head and neck squamous cell carcinoma.