Frequency ofRASMutations andPAX8/PPARγRearrangement in Follicular Thyroid Tumors in Korea

Background: Follicular thyroid tumors harbor several genetic alterations such as RAS mutations and PAX8/PPARγ rearrangement. The aims of our study were to investigate the prevalence of RAS mutations and PAX8/PPARγ rearrangement in follicular thyroid tumors and to correlate RAS mutations and/or PAX8/PPARγ rearrangement with clinicopathologic features in Korean patients with follicular thyroid carcinomas. Methods: RAS mutations were investigated by polymerase chain reaction and DNA sequencing in surgical specimens of 37 follicular thyroid carcinomas (FTCs) and 16 follicular thyroid adenomas (FTAs). PAX8/PPARγ rearrangement was analyzed by fluorescent in situ hybridization in surgical specimens of 31 FTCs and 13 FTAs. Results: RAS mutations were detected in 30% (11 of 37) of FTCs and 19% (three of 16) of FTAs. Three of 11 FTC patients with RAS mutations died of thyroid cancer, but none of the 26 FTC patients without RAS mutations. PAX8/PPARγ rearrangement was found in 10% (three of 31) of FTCs, but in none of the 13 FTAs. All three FTC patients with PAX8/PPARγ rearrangement remained in complete remission during follow-up. There were no FTC patients with both RAS mutations and PAX8/PPARγ rearrangement. Conclusion: The prevalence of RAS mutations in our series of follicular tumors was similar to previous studies. The frequency of PAX8/PPARγ rearrangements in our group of FTC was lower than previous western reports, but higher than Japanese reports. RAS mutations may be associated with hematogeneous metastasis and poor survival while PAX8/PPARγ rearrangement may be related to more favorable prognosis in Korean patients with FTCs. (Endocrinol Metab 27:45-53, 2012)