NCAM1 and neoplasm: There is now convincing evidence that NCAM-mediated neurite outgrowth, as well as tumour development and progression, critically involves the activation of fibroblast growth factor receptor 1 (FGFR1), through a cis interaction of NCAM and FGFR1.18–22 The four FGFRs and their 23 growth factor ligands control a variety of cellular processes, including development, angiogenesis, hematopoiesis and tumourigenesis.23–26 Alternative splicing of the four FGFR genes results in at least 48 receptor isoforms that vary in their ligand binding profiles and kinase domains.