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Neurotrophic tropomyosin or tyrosine receptor kinase (NTRK) genes
  1. Runjan Chetty
  1. Department of Anatomical Pathology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada
  1. Correspondence to Professor Runjan Chetty, Department of Anatomical Pathology, University Health Network, Toronto General Hospital, Toronto ON M5G 2C4, Canada; runjan.chetty{at}


The neurotrophic tropomyosin or tyrosine receptor kinase (NTRK) genes (1-3) are proto-oncogenes that when activated are encountered in a wide array of tumours. The recent advent of very specific and selective inhibitors of their gene fusions makes the NRTK gene fusions actionable. NRTK gene fusions are very characteristic of specific tumours: salivary mammary analogue secretory carcinoma, breast secretory carcinoma, infantile fibrosarcoma and congenital mesoblastic nephroma. Over 90% of these tumours bear NTRK gene fusions. While next-generation sequencing is the current platform of choice for the detection of NTRK fusions, immunohistochemistry also shows great promise. Immunohistochemical localisation of the fusion protein to the nucleus, cytoplasm, nuclear membrane and cell membrane is indicative of specific gene fusions involving the NTRK genes.

  • ntrk
  • fusion genes
  • proto-oncogenes
  • targeted therapy
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  • Handling editor Cheok Soon Lee.

  • Contributors RC is the sole author responsible for the conception and writing of the manuscript.

  • Funding The project was funded by the Academic Health Science Network NENC.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; internally peer reviewed.

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