Terminally exhausted CD8+ T cells in solid tumors: biology, biomarker potential and translational tools for precision oncology

Terminally exhausted CD8 + T cells (Ttex) are emerging as clinically relevant immune subsets across solid tumors, marked by sustained inhibitory receptor expression, loss of TCF1, and limited proliferative capacity. Once considered functionally inert, Ttex are now recognized for their residual cytotoxic potential and strong associations with tumor immunogenicity, including microsatellite instability (MSI), high tumor mutational burden (TMB), and neoantigen load. Importantly, the prognostic significance of Ttex is highly tumor-context-dependent, shaped by stromal architecture, mutational burden, and progenitor Tpex availability. This review examines the biology, spatial localization, and prognostic value of…