Fusions of NTRK1, NTRK2, and NTRK3 and their partner genes can lead to overexpression of Trk proteins, which in turn activate downstream signaling pathways, such as RAS/MAPK, PI3K/AKT, and PLC-γ, causing transformation, proliferation, and survival of cancer cells. The gene discussed is NTRK3; the disease is cancer.