MKI67 and head and neck squamous cell carcinoma: We used a five-color multiplex immunohistochemistry (IHC) Opal panel to distinguish tumor-resident (CD103+), recruited (CD103–), proliferating (Ki67+) and non-proliferating (Ki67−) CD8+T cells within tumor stroma and tumor fields of 12 HPV-negative HNSCC resection specimens (figure 1B, online supplemental figure 2).