AIMS: Follicular thyroid carcinoma (FTC) has been a diagnostic challenge for decades. The PAX8-PPARã rearrangement has been detected in FTC and classic papillary thyroid carcinomas (PTCs). The aims of this study were to assess the presence of PAX8-PPARã by using tissue microarrays in a large cohort of different thyroid neoplasms, and to assess its diagnostic and prognostic implications.METHODS AND RESULTS: Fluorescence in-situ hybridization (FISH) analysis for PAX8-PPARã was performed on 226 thyroid tumours, comprising FTCs (n = 59), PTCs (n = 126), poorly differentiated thyroid carcinomas (PDs; n = 34), follicular thyroid adenomas (FTAs; n = 5), and follicular tumours of unknown malignant potential (FTUMPs; n = 2). PAX8-PPARã was detected in 12% of FTCs, 1% of PTCs, 7% of PDs, and in both cases of FTUMP. There was no correlation between the extent of capsular or vascular invasion and PAX8-PPARã, or between lymph node or haematogenous metastasis and PAX8-PPARã. Overall survival (OS), tumour-specific survival (TSS) and relapse-free-survival (RFS) were not influenced by PAX8-PPARã.CONCLUSIONS: In this study, we demonstrate for the first time the presence of PAX8-PPARã in PDs and FTUMPs, whereas in FTCs and PTCs the prevalence of PAX8-PPARã is lower than previously reported. PAX8-PPARã did not correlate with invasiveness or affect prognosis in any tumour type.
Adenocarcinoma, Follicular Adenoma