NGF and Merkel cell skin cancer: Predominant TrkAIII mRNA expression in advanced stage and recurrent MCPyV positive MCCs, with evidence of intracellular TrkAIII expression and activation, also extends previous reports of a potential oncogenic role for TrkA in MCC [14, 15] but would negate a proposed requirement for NGF-expressing MCC-infiltrating inflammatory cells for activation [15], which may be more relevant to MCPyV negative MCCs, BCCs and SCCs that express fully spliced TrkA receptors (this study, [37, 38]).