RET/PTC rearrangements arising from a small population of papillary thyroid carcinoma cells, possible candidate for passenger mutation..     ///    "However, the prevalence of RET/PTC differs considerably among investigators, and its impact on cancer progression has been controversial. "    ///    "Even though RET/PTC is a specific genetic event in the carcinomas, our results suggested the possibility of RET/PTC as ""passenger"" abnormalities rather than ""driver"" oncogenic mutation during thyroid cancer progression, warranting further studies on mechanisms and implication of RET gene instability.. "    ///    The remaining seven tumors with split RET signals had no RET/PTCs amplicon.     ///    "Among tumors with split RET signals, 36.4% (4/11) of tumors exhibited detectable messenger RNA of RET/PTC1 or RET/PTC3. "    ///    "In conclusion, the current study disclosed that RET/PTCs occur in a small population of tumor cells in papillary thyroid carcinomas. "    ///    "In RT-PCR analysis, RET/PTC was found in 28.6% (4/14) of tumors. "    ///    "FISH DNA probes included RET locus, and PCR primers were designed targeting RET/PTC1 or RET/PTC3. "