Steroid-Refractory Lichenoid Eruption Associated with Pembrolizumab in a Patient with Non-Small Cell Lung Cancer.

Programmed cell death receptor 1 (PD-1) inhibitors are promising and effective treatments for various cancers. Cutaneous adverse events, such as lichenoid drug eruptions, are well-known common side effects associated with PD-1 inhibitors. Lichenoid drug eruptions associated with PD-1 inhibitors show rapid improvement with high potency topical steroids and do not require cessation of the offending drug. We present the case of an 84-year-old female with progressive pembrolizumab therapy-associated lichenoid eruption that was resistant to several treatments and ultimately required discontinuation of pembrolizumab and treatment with methotrexate to resolve. This report includes histological findings of the pembrolizumab-associated lichenoid eruption.