Merkel Cell Carcinoma of Unknown Primary: Immunohistochemical and Molecular Analyses Reveal Distinct UV-Signature/MCPyV-Negative and High Immunogenicity/MCPyV-Positive Profiles.

Our results showed distinct UV-signatures in MCPyV-negative tumors and high immunogenicity in MCPyV-positive tumors. Although additional studies are warranted for the MCPyV-positive cases, our findings are supportive of a cutaneous metastatic origin for MCPyV-negative MCC-UP tumors.