Tyrosine kinase receptors (Trk) play an important role in the development and clinical behaviour of NB.323 The Trk family consists of 3 Trks: Trk A, B and C. High expression of Trk A is associated with a good prognosis, with tumours displaying favourable features and is seen in tumours that spontaneously regress.323,324 On the other hand, high Trk B expression is associated with features such as MYCN amplification and unfavourable features and prognosis. This evidence concerns the gene NTRK1 and neoplasm.