[Clinicopathological significance of DICER1 mutation in follicular thyroid carcinoma].

<b>Objective:</b> To investigate the clinical and pathological significance of the DICER1 mutation in follicular thyroid carcinoma (FTC). <b>Methods:</b> Sixty-eight cases of primary FTC resected between 2009 and 2023 were retrieved from The Affiliated Hospital of Qingdao University, Qingdao, China. Sanger sequencing was performed to identify DICER1 and TERT promoter mutations in all cases. Cases with DICER1 or TERT promoter mutations were subject to additional examination of potential mutations in KRAS, HRAS, and NRAS. The clinical and pathological features of DICER1-mutant FTCs were then analyzed. The relationship between DICER1 mutations and TERT-promoter/RAS mutations was also assessed. <b>Results:</b> DICER1 mutations were detected in 16 of the 68 FTC cases (23.5%), with 11 near E1813 at exon 25, 6 near D1709 at exon 24, and 1 in the splice region of exon 25. Two cases harbored two (distinct) mutations. All patients with DICER1-mutant FTC were female. Compared with patients with DICER1-wild-type FTC, those with DICER1-mutant were much younger, and had a higher proportion of minimally invasive subtype. Nine FTCs with DICER1 mutations were subject to further sequencing on adjacent non-cancerous tissues or lymph node tissues, but no mutations were detected. TERT-promoter or RAS hotspot mutations were not identified in any of the DICER1-mutant cases. However, TERT-promoter mutation was found in 6 DICER1-wild-type cases (8.8%, 6/68), with 3 cases also having RAS hotspot mutations and exhibiting highly aggressive biological behaviors. <b>Conclusion:</b> DICER1 mutations may occur in FTCs and appear mutually exclusive with RAS and TERT-promoter mutations, warranting further study as RAS-like mutations.