Tumor-associated macrophages (TAMs), subsets of granulocytes, myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs), natural killer (NK) cells, and mast cells are examples of accessory cells of the native immune system, while different T lymphocyte subpopulations, such as CD4+ T cells, CD8+ T cells, regulatory T cells (Tregs), and B lymphocytes, are examples of cells of the adaptive immune system that can infiltrate the TME. This evidence concerns the gene CD4 and neoplasm.