CTLA4 and mucosal melanoma: Ipilimumab, an antibody that blocks the cytotoxic T-lymphocyte antigen-4 (CTLA-4) immune checkpoint, is approved by the United States Food and Drug Administration (FDA) in 2011 based on an overall survival (OS) advantage in patients with metastatic melanoma, however its efficacy in mucosal melanoma is not clear yet [31].