APOBEC3C and APOBEC3G levels were higher in MCPyV+ MCCs compared with MCPyV− MCCs, and APOBEC3G showed statistically significant coexpression with LT, which could implicate an immune response to MCPyV infection and make APOBEC3C and APOBEC3G potential LT mutators. The gene discussed is APOBEC3C; the disease is infection.