Immune cells in the tumor microenvironment contain regulatory T cells (Treg), CD8+ T cells, CD4+ T cells, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), natural killer (NK) cells, and cancer-associated fibroblasts (CAFs), which contribute to inducing immune evasion, EMT, and drug resistance. This evidence concerns the gene CD8A and neoplasm.