Frequency of RAS Mutations and PAX8/PPARgamma Rearrangement in Follicular Thyroid Tumors in Korea

ABSTRACT

BACKGROUND: Follicular thyroid tumors harbor several genetic alterations such as RAS mutations and PAX8/PPARgamma rearrangement. The aims of our study were to investigate the prevalence of RAS mutations and PAX8/PPARgamma rearrangement in follicular thyroid tumors and to correlate RAS mutations and/or PAX8/PPARgamma 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/PPARgamma 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/PPARgamma rearrangement was found in 10% (three of 31) of FTCs, but in none of the 13 FTAs. All three FTC patients with PAX8/PPARgamma rearrangement remained in complete remission during follow-up. There were no FTC patients with both RAS mutations and PAX8/PPARgamma rearrangement. CONCLUSION: The prevalence of RAS mutations in our series of follicular tumors was similar to previous studies. The frequency of PAX8/PPARgamma 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/PPARgamma rearrangement may be related to more favorable prognosis in Korean patients with FTCs.