Tislelizumab-induced lichenoid drug eruption and cutaneous squamous cell carcinoma: a rare dermatologic immune-related adverse event.

Anti-programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors have made significant advances in the field of immunotherapy, revolutionizing the treatment of metastatic cancers. These immune checkpoint inhibitors have been approved by the U.S. Food and Drug Administration for a wide range of malignancies. However, as the clinical use of PD-1/PD-L1 inhibitors has expanded, concerns have arisen regarding immune-related adverse events (irAEs). Among these, skin reactions can manifest as atypical, non-specific lesions, including vitiligo, eczema, psoriasis, and other cutaneous changes. Severe manifestations, such as life-threatening rashes, may also occur. Here, we report a case of a patient with non-small cell lung cancer (NSCLC) who developed two distinct patterns of skin lesions after treatment with tislelizumab, a PD-1 inhibitor. The lesions, diagnosed as lichenoid drug eruption and squamous cell carcinoma in situ, resolved completely after treatment with systemic glucocorticosteroids and antihistamines. Notably, the patient’s condition did not recur upon subsequent administration of the same targeted therapy. This case underscores the importance of recognizing rare cutaneous adverse reactions to PD-1/PD-L1 inhibitors, highlighting the need for prompt diagnosis and proactive management to minimize the risk of missed diagnoses and disease progression.