The granulomatous pulmonary nodules induced by tislelizumab in advanced squamous NSCLC: a case report with challenging differential diagnosis.

Background: Immune checkpoint inhibitors (ICIs), such as the programmed death-1 (PD-1) inhibitor, have revolutionized the treatment of advanced non-small cell lung cancer (NSCLC), leading to remarkable improvements in survival and long-term disease control. Despite the aforementioned advances, the clinical application of ICIs remains frequently associated with immune-related adverse events (irAEs), which have the potential to affect multiple organ systems. irAEs involving the lungs, particularly granulomatous inflammation, remain rare and diagnostically challenging. Case Description: A 59-year-old Chinese male with stage IVA squamous NSCLC developed new pulmonary nodules after three cycles of tislelizumab combined with chemotherapy. Initial suspicion of infection led to empirical anti-tuberculosis therapy, but biopsy confirmed non-caseating granulomatous inflammation without evidence of infection. Corticosteroid treatment resulted in rapid resolution of the nodules. Reintroduction of tislelizumab with tapering hormone maintained disease control, but a transient new nodule emerged after steroid cessation, which later resolved spontaneously. The patient's progression-free survival (PFS) was 46 months, significantly longer than the median PFS patients with advanced squamous cell carcinoma. Conclusions: This case highlights the diagnostic complexity of ICI-induced granulomatous lung lesions, their steroid responsiveness, and the feasibility of ICIs rechallenge under close monitoring. Pathological confirmation is crucial for the diagnosis, and could avoid unnecessary anti-infective therapy.