Lichenoid dermatitis in three patients with metastatic melanoma treated with anti-PD-1 therapy.

Therapies that activate the immune system through blocking the binding of programmed death ligand 1 (PD-L1) present on tumors and PD-1 (programmed death 1) present on activated immune cells are revolutionizing the care for patients with cancer. These therapies work by inhibiting negative regulators of the immune system, thereby decreasing a tumor's ability to evade the immune system. The side effects of anti-PD-1/PD-L1 therapies are generally mild and as expected are related to autoimmune reactions.