Our findings reopen the debate on which marker, PD-1 or CD137, best identifies the repertoire of tumour-specific T lymphocytes.11,12 In the only patient studied, Ye et al. found that PD-1+CD137+ cells, but not the PD-1+CD137− subset, harboured tumour-specific T cells in OC.12 These results appear to contradict Rosenberg group’s findings in melanoma,11 which showed that both populations comprised tumour-specific CD8 TILs. Here, TNFRSF9 is linked to melanoma.