Merkel Cell Carcinoma (MCC) is a rare but deadly skin cancer. Its incidence is increasing in the elderly and in immunosuppressed populations. In 2008 a polyomavirus, MCPyV, was identified as a likely causal agent, a finding replicated in many laboratories. We showed that the seroprevalence of MCPyV was 65-80% in the general population. However, antibodies to the MCPyV T antigens were restricted to cases with MCC. Importantly a rise in the titer of these antibodies could predict recurrence. Some patients were shown to have CD8+ T cells directed towards T antigen epitopes. Expansion of tetramer-isolated MCPyV specific T cells was developed for immunotherapy. We will present data for one patient with increasing T antigen titers who was shown to have pancreatic metastases. Following treatments to upregulate HLA expression and infusions of MCPyV specific T cells metastatic lesions regressed. These data indicate that immunotherapeutic approaches to eliminate MCPyV expressing tumor cells can improve patient outcomes.