Background: Immune checkpoint inhibitors (ICI) have significantly improved cancer prognosis but can lead to immune-related adverse events (irAE), including cutaneous manifestations affecting 30% to 60% of ICI-treated patients. However, the physiopathology of cutaneaous irAE remains unclear. Objective: This study investigated the immune infiltration in tissues affected by cutaneous irAE to elucidate their contribution to the pathogenesis of these toxicities. Methods: Skin biopsies from 6 patients with ICI-induced lichenoid eruptions were compared using imaging mass cytometry to samples from 7 controls with non-drug-related lichen planus. Results: T cells were the predominant cell type within the inflammatory infiltrate in all samples, but we observed a reduced T-cell infiltration and an increased B-cell frequency in ICI-induced lichen planus compared to non-drug related lichen planus. Among B cells, we observed a significant decrease in IgD-CD27- double-negative B cells and an increase in IgD+CD27- naive B cells. Spatial analysis demonstrated that infiltrating B cells were organized in aggregates close to T cells in ICI-induced lichen planus. Limitations: This is a retrospective single-center study with a relatively small sample size. Conclusion: This study sheds light on the involvement of B cells in the pathogenesis of ICI-induced lichen planus, suggesting distinct immunological mechanisms from non-drug-related lichen planus.

B-Cell Involvement in Immune Checkpoint Inhibitor-Induced Lichen Planus: A Comparative Analysis with Non-Drug-Related Lichen Planus.