CD7 and post-transplant lymphoproliferative disease: An Epstein-Barr virus (EBV)-associated second tumor was also observed in several studies: our group reported a patient diagnosed with EBV-associated diffuse large B cell lymphoma (DLBCL) on day 55 after CD7 CAR-T cell therapy, who eventually died of disease progression [13]; Chen et al. reported a case of EBV reactivation and post-transplant lymphoproliferative disease (PTLD) post-CD7 CAR-T cell infusion [23]; Two cases of EBV-associated PTLD were also reported in a CD5 CAR-T cell clinical study, and both died from treatment complications [9].