Temporal association of diffuse large B-cell lymphoma with PD-1 inhibitor therapy in a patient with gastric adenocarcinoma: a case report

This case illustrates a temporal association between PD-1 inhibitor-based therapy and the diagnosis of DLBCL. Given the lack of baseline systemic staging, overlapping PET/CT findings, early diagnostic uncertainty in effusion cytology, and potential contributions from chemotherapy-induced immune perturbation and EBV-associated processes, a direct causal relationship cannot be established. This report underscores the importance of comprehensive baseline evaluation and cautious interpretation of atypical lymphoid findings during immunotherapy.