The RET/PTC rearrangements were found in PTC from children contaminated by the Chernobyl fall-out as well as in tumours from patients with a history of therapeutic external radiation, with a frequency of 60-84%.     ///    The other forms of RET/PTC were observed in only a minority of the post-Chernobyl PTC (< 20%).     ///    "In two of the post-therapeutic radiation PTC, RET/PTC1 and PTC3 were simultaneously present. "    ///    "These ret chimeric genes which are due to intra- or inter-chromosomal translocations, were called RET/PTC1 to PTC5. "