DICER1 mutations in Bethesda III/IV thyroid cytology samples: A multicenter observational study.

Mutations in DICER1 are uncommon, poorly understood, and infrequently found in thyroid nodules. The objective of this study was to investigate category III/IV thyroid nodules according to The Bethesda System for Reporting Thyroid Cytopathology with DICER1 gene mutations detected in fine-needle aspiration cytology samples using ThyroSeq v3 molecular testing, with a focus on an exploration of the clinical and histopathologic outcomes of these nodules. In this multicenter study spanning more than 6 years, nodules were retrospectively analyzed for patient demographics, clinical course, cytologic features, and histopathology, where available. In total, 88 patients with somatic DICER1 mutations were included, with a mean age of 39.6 years and a female predominance. All mutations were in the somatic hotspot region, most commonly at the codon 5437 site. Most excised nodules showed benign histologic features (65.9%). Interestingly, the rate of malignancy was higher in this cohort compared with that in the national average. DICER1 mutations appear to confer a higher risk of malignancy, but are not associated with any specific cytological or histopathological distinguishing features.