Pembrolizumab-Induced Lichen Planus in a Patient with Metastatic Pulmonary Giant Cell Carcinoma: A Case Report and Literature Review

Abstract

Ιmmune checkpoint inhibitors (ICIs) have revolutionized the management of advanced cancers. Nevertheless, the oncologic response is often achieved at the cost of immune-related adverse events (irAEs). We present a case of an immune-mediated lichen planus (LP) and a literature review of similar cases. A 60-year-old man, who is being treated with pembrolizumab for a pulmonary giant cell carcinoma since April 2022, presented in November 2022 with a pruritic eruption that appeared two weeks ago. Examination showed bright purple confluent scaly papules on wrists, proximity of limbs, back and buttocks and palmar keratoderma made of violaceus papules covered with reticular white striae. Histological examination revealed an epidermal hyperplasia, vacuolization of the basal layer, necrotic keratinocytes and a band-like subepidermal lymphocytic infiltrate with many eosinophils. The diagnosis of an immune-related LP was retained. Pembrolizumab was withheld because of the severity and the extension of the lesions. Superpotent topical steroids were prescribed with a significant improvement of the rash within 3 weeks. Immune-mediated lichenoid euptions represent one of the most frequent dermatologic irAEs. In our patient, the onset seven months after the initiation of ICIs, the infiltrate rich in eosinophils, and the rapidly diffused character are indications of an immuno-mediated LP.