RET REARRANGEMENTS IN JAPANESE PEDIATRIC AND ADULT PAPILLARY THYROID CANCERS

Oncogenic rearrangements of the vet proto-oncogene (ret/PTC) are found uniquely in papillary thyroid carcinomas. The prevalence of ret/PTC i n these tumors varies widely, from 0% to 87%, among patient series fro m different geographical regions. The differences in the prevalence of vet rearrangement have been ascribed to age, genetic, and/or environm ental factors. The very high prevalence of ret/PTC in tumors arising i n children after the Chernobyl nuclear accident has generated speculat ion that this oncogene may be an indicator of overt or inadvertent rad iation exposure. In Japan, the prevalence of vet activation is reporte dly quite low (0% to 9%). Here we examined the frequency of vet rearra ngements in papillary carcinomas from Japanese adults and children by means of reverse transcription polymerase chain reaction (RT-PCR) foll owed by Southern hybridization. Ref rearrangements were detected in 4 of 11 (36%) tumors from the adult population, and in 3 of 10 (30%) ped iatric tumors. One child with a solid variant papillary carcinoma had a ret-PTC3 rearrangement, further supporting the association between t he solid variant histotype and this particular rearrangement of vet. T he present data do not support a major geographic difference in the pr evalence of ret/PTC rearrangements in papillary carcinomas between Jap an, the United States, and Italy.