Original Abstract
BACKGROUND: Tislelizumab, a specific immune checkpoint inhibitor (ICI) targeting the programmed death protein-1 (PD-1) receptor, represents a novel immunotherapeutic approach for non-small cell lung cancer and has shown promising therapeutic potential. With the increasing clinical use of ICIs, immune-related adverse events (irAEs), including pneumonitis, thyroiditis, and pancreatitis, have been widely recognized. However, pleuritis presenting as pleural effusion (PE) in patients treated with tislelizumab has not yet been reported. CASE PRESENTATION: Here, we report the case of a 60-year-old man with primary lung squamous cell carcinoma who developed a new-onset PE. The patient had previously received treatment with tislelizumab, cisplatin, nab-paclitaxel, and radiotherapy. Notably, he had not received any systemic treatment during the six months preceding the onset of PE. Repeated thoracocenteses showed no malignant cells in the pleural fluid. Further evaluation, including medical thoracoscopy, showed no evidence of malignancy or radiation-induced pleuritis. Additionally, the PE was successfully controlled after corticosteroid therapy. CONCLUSION: This case suggests that late-onset PE may represent a rare form of irAE associated with ICIs and highlights the importance of continued monitoring for delayed irAEs during long-term tumor immunotherapy.