Pembrolizumab‐induced pseudoepitheliomatous eruption consistent with hypertrophic lichen planus

Abstract

Pembrolizumab, an anti-programmed cell death-1 (PD-1) antibody preparation, has been shown to induce various dermatologic adverse events which may present with delayed onset or even after discontinuation of therapy. We report a 78-year-old female patient with a stage II lung adenocarcinoma treated with pembrolizumab, who developed lichenoid eruptions and multiple cutaneous plaque/nodular eruptions as pseudoepitheliomatous hyperplasia, during and up to 2 months after discontinuation of pembrolizumab therapy. Multiple skin biopsies revealed epidermal hyperplasia with hyperkeratosis, hypergranulosis, diffuse to patchy lichenoid lymphocyte infiltrate with scattered eosinophils and neutrophils, confluent to scant dyskeratosis of the lower epidermis, minimal to overt invagination, and cystic proliferation of squamous epithelium to papillomatosis with hypergranulosis and keratosis. Overall, multiple patterns were present with similarities to lichenoid drug eruption, lichen planus, early invasive squamous cell carcinoma, early keratoacanthoma, and verruca. However, the findings ultimately supported a diagnosis of hypertrophic lichen planus. All the lesions resolved with oral prednisone, hydroxychloroquine, and topical triamcinolone acetonide ointment 0.1%. In summary, our case shows that pembrolizumab can induce lichenoid eruption with pseudoepitheliomatous hyperplasia, and these lesions can clinically and pathologically mimic early invasive squamous cell carcinomas or keratoacanthomas. K E Y W O R D Shypertrophic lichen planus, PD-1, pembrolizumab, pseudoepitheliomatous hyperplasia

Nonhealing hyperkeratotic plaques in a lung cancer patient: what caused it?

“…There have been previous reports of PEH being mistaken for squamous cell carcinoma (SCC) 7,8 . A recent report highlights a patient on pembrolizumab with lesions that clinically and pathologically mimicked SCC and keratoacanthomas but were found to be hypertrophic lichen planus 9 . Another report of PEH with lichenoid inflammation, interface change, and hypergranulosis was recently reported in a patient on avelumab, which is an anti‐PD‐L1 therapy 10 …”

Hypertrophic lichenoid dermatitis during pembrolizumab treatment

“…1 Lichenoid dermatitis and its hypertrophic variant are also reported as cutaneous irAEs. [2][3][4] Hypertrophic lichenoid dermatitis should be distinguished from well-differentiated squamous cell carcinoma (SCC) because of their clinical and histological similarities. 2,3 In the present case, a differential diagnosis from SCC was needed because the architecture of the acanthosis resembled downward growth of SCC.…”

“…[2][3][4] Hypertrophic lichenoid dermatitis should be distinguished from well-differentiated squamous cell carcinoma (SCC) because of their clinical and histological similarities. 2,3 In the present case, a differential diagnosis from SCC was needed because the architecture of the acanthosis resembled downward growth of SCC. However, a diagnosis of SCC could be excluded because the cellular atypia of keratinocytes was not obvious and his skin lesions improved with topical corticosteroids.…”

Eosinophilic infiltration discriminates lichen‐planus‐like eruption caused by an immune checkpoint inhibitor from ordinary lichen planus

“…Only a few reports describe eosinophilic infiltration in ICI-induced LP-like eruption, but do not focus on this finding. 4 Shi et al 5 reviewed 20 cases of lichenoid reaction caused by ICIs and noted that only four had elevated peripheral blood eosinophil counts. Considering that our three patients did not have eosinophilia, the lesional eosinophilic infiltration in the LP-like eruption caused by ICIs may not be closely associated with circulating eosinophilia.…”