Pembrolizumab (Keytruda)

Pembrolizumab (Keytruda) has been shown to induce a variety of dermatologic adverse events including maculopapular eruption, lichenoid dermatitis, pruritus, vitiligo, and eruptive keratoacanthomas. An elderly patient with pulmonary adenocarcinoma treated with Pembrolizumab, who subsequently developed lichenoid eruptions and multiple cutaneous pseudoepitheliomatous hyperplasia.  Up to eight skin biopsies are studied.  The lesions are ranged from pseudoepitheliomatous 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.