In an attempt to categorize the intrinsic heterogeneous nature of metastatic melanoma, Halse and colleagues used multiplex immunohistochemistry to provide a model which defines the immune context into four categories, using the presence or absence of PD-L1+ melanoma cells and/or macrophages, and their location within or around the tumor, combined with the presence or absence of intratumoral CD8+ T cells. The gene discussed is CD8A; the disease is melanoma.