Case Report of Multiple Keratoacanthomas and Squamous Cell Carcinomas in a Patient Receiving Pembrolizumab.

: PD-1 is expressed on antigen-stimulated T cells and induces a downstream signaling pathway that works by negative feedback to inhibit T cell proliferation, cytokine release, and cytotoxicity. PD-1 antibodies increase tumor cell killing peripherally and have a role in advanced melanoma treatment. We describe a case of an 84 year old female with stage 4 metastatic melanoma in a trial of the PD-1 inhibitor pembrolizumab who developed multiple keratoacanthomas after several months of treatment. While keratoacanthomas have been reported in patients taking BRAF inhibitors, no such reports exist for those on pembrolizumab, making this the first case report to point out this association for further investigative studies. J Drugs Dermatol. 2017;16(5):513-515. .