Here we discuss a specific family of such receptors and downstream signaling molecules, the tyrosine kinase receptors and the cytoplasmic molecules they activate, some of them, such as RAF being serine/threonine kinases but directly activated in tyrosine kinase receptor pathways, their role in normal cell proliferation and their role as targets for molecules designed to control cell proliferation in cancer. This evidence concerns the gene NTRK1 and cancer.