Prevalence and distribution of ret/ptc 1, 2, and 3 in papillary thyroid carcinoma in New Caledonia and Australia.

The world's highest incidence of thyroid cancer has been reported among females in New Caledonia, a French overseas territory in the Pacific located between Australia and Fiji. To date, no molecular genetic studies in this population are available. Over the past few years, the oncogenic rearrangement of the ret protooncogene (ret/ptc) has been studied in papillary carcinomas in different populations. In this study, we investigated the prevalence and distribution of ret/ptc1, 2, and 3 in papillary thyroid carcinoma from the New Caledonian population and compared the pattern with that of an Australian population. Fresh-frozen and paraffin-embedded papillary carcinomas from 27 New Caledonian and 20 Australian patients were examined for ret rearrangements by means of RT-PCR with primers flanking the chimeric region, followed by hybridization with radioactive probes. ret/ptc was present in 70% of the New Caledonian and in 85% of the Australian samples. Multiple rearrangements were detected and confirmed by sequencing in 19 cases, 4 of which had 3 types of rearrangements in the same tumor. This study demonstrates a high prevalence of ret/ptc in New Caledonian and Australian papillary carcinoma. The findings of multiple ret/ptc in the same tumor suggest that some thyroid neoplasms may indeed be polyclonal.