In this study, tissue microarrays (TMA) constructed from formalin-fixed, paraffin-embedded (FFPE) tissue blocks of HNSCC primary tumor and/or lymph node metastasis, and stained with different commercial IVD PD-L1 immunohistochemical assays were reviewed by a pool of trained pathologists to assess CPS. The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.