NTRK1 and Merkel cell skin cancer: The lack of phosphorylated TrkA immunoreactivity in the MCPyV negative MCC and in BCC, SCC, and normal skin tissues exhibiting exclusive fully spliced TrkA mRNA expression and TrkA immunoreactivity confirms a marked difference in TrkA isoform phosphorylation status in MCPyV positive MCCs and MCPyV negative MCC, BCCs, SCCs and normal skin, and indicates that fully spliced TrkA in BCC, SCC and normal skin is either inactive or activated below the threshold of detection in FFPE tissues.