Furthermore, TILs can be classified according to their phenotype and biological function as CD8+ T cells, CD8+ tissue-resident memory T (TRM) cells, CD4+ T helper 1/2/17 (Th1, Th2, and Th17) cells, CD4+ regulatory T cells (Treg, defined by the expression of Forkhead Box P3 protein [FOXP3]), CD4+ follicular helper (Tfh) T cells, and tumor-infiltrating B cells [10]. Here, FOXP3 is linked to neoplasm.