NTRK1 and Merkel cell skin cancer: Consistent with this, MCPyV positive MCCs also exhibited a significantly lower 19.49 ± 19.71% (mean ± SD) TrkA percentage total TrkA expression compared to 99.48 ± 0.41% in MCPyV negative MCC, BCCs, SCCs and normal skin (P < 0.0001, df = 24) (Fig. 1b, Table 2).