To investigate the distribution of the MΦ markers CD68 and CD163 within the tumor microenvironment of head and neck squamous cell carcinoma (HNSCC), whole slides of HPV-associated, non-HPV-associated oropharyngeal cancer and tonsils as tumor-free controls were sequentially stained using antibodies against CD68, CD163, CK, CD45 and Ki-67 (Figure 1A). Here, CD68 is linked to neoplasm.