CD4 and neoplasm: A complex and dynamic network is constructed by tumor-infiltrating lymphocytes (TILs), including cytotoxic CD8+ T cells, CD4+ Teffs, T regulatory cells (Tregs), B cells, tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and non-immune cells, including cancer-associated fibroblasts (CAFs) and tumor endothelial cells (TECs).