Immune checkpoint molecules such as PD-1 [23], CTLA-4 [24], T cell immunoglobulin and mucin domain-3 (TIM-3) [25], and lymphocyte-associated gene 3 (LAG-3) [26] have been found to be expressed in several immune cell types, including T cells, natural killer (NK) cells, B cells, dendritic cells, tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs). This evidence concerns the gene HAVCR2 and neoplasm.