Lenvatinib is a TKI inhibiting VEGFR-1, 2, and 3, fibroblast growth factor receptor (FGFR)-1–4, platelet-derived growth factor receptor (PDGFR), RET and KIT signalling pathways, that has been approved for the treatment of differentiated thyroid cancer, but only scanty data exist on its use in MTC. This evidence concerns the gene RET and thyroid cancer.