Oral lichenoid lesions as an immune‐related adverse event: A rare case report and literature review

Background Reports of oral lichenoid lesions (OLLs) as an immune‐related adverse event (irAE) are rare. Case presentation An 81‐year‐old man was visited with a complaint of severe pain in the oral mucosa. He had received nivolumab for relapsed malignant melanoma. Pathological examination showed acanthotic and destructive changes in the epithelium with inflammatory infiltrates and CD8 positivity. Based on these findings, the diagnosis was OLL as an irAE. Oral prednisolone was started, and the lesion gradually resolved. Conclusion The literature review suggested that OLL can appear as an irAE on the buccal mucosa and tongue after a varying number of cycles of immune checkpoint inhibitors. Routine surveillance of the oral mucosa is needed.