NTRK1 and cancer: We propose that detection alternative Δ exon 6–7 TrkAIII identifies an MCC subgroup that may benefit from novel inhibitors of MCPyV T-antigen and Δ exon 6–7 TrkAIII expression or clinically approved Trk kinase inhibitors such as larotrectinib and entrectinib, known to inhibit mutation and deletion-activated TrkA oncogenes and to elicit durable responses in a wide range of advanced-stage TrkA-fusion oncogene-driven cancers [37,38,39], supporting the call for a large multicentre study.