Clinical and pathomorphological features of rare immune-related dermatological adverse events of immune checkpoint inhibitors in cancer patients

Objective - to evaluate the clinical and pathomorphological features of rare immune-related dermatological adverse events (sarcoid-like, vitiligo-like and scleroderma-like reactions) in cancer patients receiving PD-1/PD-L1 immune checkpoint inhibitor therapy. Materials and methods. An open prospective single-center study included 204 patients treated with PD-1/PD-L1 immune checkpoint inhibitors in 2023-2026. The clinical form was established on the basis of the clinical presentation and histopathological examination. Histopathological examination of skin biopsies (punch biopsy, hematoxylin and eosin staining, light microscopy) was performed in 54 patients. Results. Among immune-related dermatological adverse events, maculopapular, lichenoid and psoriasiform eruptions predominated, whereas sarcoid-like, vitiligo-like and scleroderma-like reactions were rare (vitiligo-like depigmentation - n=3 (5,5%); scleroderma-like reaction - n=2 (3,7%); sarcoid-like reaction - n=1 (1,8%)). Each form reproduced the morphology of the corresponding dermatosis while retaining features of a drug-induced, immune-mediated process: sarcoid-like - non-necrotizing epithelioid-cell granulomas with Pirogov-Langhans giant cells; vitiligo-like - complete absence of melanocytes in the basal layer; scleroderma-like - epidermal atrophy, diffuse dermal sclerosis and hyalinization with loss of skin adnexa. Conclusion. Rare irDAE subtypes display characteristic clinicopathological features and warrant mandatory histopathological verification, which holds both diagnostic and prognostic significance and helps prevent the unwarranted discontinuation of life-saving antitumor immunotherapy.

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