RET-PTC 3 transgenic mice give rise to thyroid tumours with a more solid phenotype than those seen in RET PTC1 transgenic mice, and in vitro RET-PTC3-transfected cells show a higher growth rate than RET-PTC 1-transfected cells (Santoro et al, 1996; Powell et al, 1998; Basolo et al, 2002). Here, RET is linked to thyroid tumor.