The extracellular domain of Trk binds the ligand, leading to activation of the tyrosine kinase, phosphorylation (pTyr) of the Trk intracellular domain, and signal transduction cascades involving kinases mitogen-activated protein kinase (MAPK) and AK mouse thymoma (Akt) [7] that are activated by phosphorylation. Here, NTRK1 is linked to thymoma.