Merkel Cell Carcinoma: Updates on Pathogenesis, Diagnosis, and Management

Purpose of Review To describe updates on the pathogenesis, diagnosis, and management of Merkel cell carcinoma (MCC). Recent Findings Sequencing studies revealed that MCCs have either a low mutational burden and integrated Merkel cell polyomavirus (MCPyV), or they have a high number of ultraviolet-associated somatic mutations and no MCPyV. Clinically, prognosis was better for stage III MCC of unknown primary than known primary. Similarly, lack of immunosuppression conferred better prognosis. The immunogenicity of MCC was reflected in high response rates to PD-1/PD-L1 checkpoint inhibitors. Summary MCC is a rare but aggressive neuroendocrine skin cancer associated with advanced age and immunosuppression. Approximately 80% of MCCs are MCPyV driven, whereas MCPyV-negative tumors have mutations in genes such as p53 and RB1 . MCC is highly immunogenic, and recently, the anti-PD-L1 antibody avelumab was approved to treat metastatic MCC. Here, we summarized features of the pathogenesis, diagnosis, and management of MCC.