Purpose

This phase II trial studies how pembrolizumab works before and after surgery in treating patients with stage III-IV high-risk melanoma. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving pembrolizumab before and after surgery may work better compared to after surgery alone in treating melanoma.