Involvement of the PAX8/peroxisome proliferator-activated receptor γ rearrangement in follicular thyroid tumors

Recently, a translocation t(2;3)(q13;p25), involving the fusion of PAX8 and peroxisome proliferator-activated receptor gamma (PPARgamma) was suggested to arise only in follicular thyroid carcinomas. In this study, a group of 87 thyroid tumors were analyzed to determine the involvement of the PAX8/PPARgamma fusion gene in these tumors, and also to determine whether this rearrangement can be used as a diagnostic marker for the differentiation between follicular thyroid carcinoma and adenoma. The PAX8/PPARgamma rearrangement was detected by RTPCR, fluorescence in situ hybridization, and/or Western analysis in 10 of 34 (29%) follicular thyroid carcinomas and in one of 20 (5%) atypical follicular thyroid adenomas, but not in any of the 20 follicular thyroid adenomas or 13 anaplastic thyroid carcinomas studied. In addition, seven of the 87 thyroid tumors exhibited involvement of PPARgamma alone. Our findings suggest that PAX8/PPARgamma occurs frequently in follicular thyroid carcinomas, and the presence of this rearrangement is likely to prove highly suggestive of a malignant tumor. Lack of the PAX8/PPARgamma rearrangement in the anaplastic thyroid carcinoma group suggests that the tumorigenic pathway in these tumors is likely to be independent of this fusion. Furthermore, the results suggest that other rearrangements, involving PPARgamma and other unidentified genes, may be involved in follicular thyroid tumorigenesis.