CD4 and chordoma: It is well established that increased immune infiltration is conducive to more favorable prognosis in many types of cancers such as melanoma, head and neck, breast, bladder, urothelial, ovarian, renal, prostatic, lung, chordoma, and colorectal cancer (26, 33–35), and infiltrating immune cells mainly consist of the T lymphocyte family, such as CD8+ T cell and CD4+ T cell (36–39).