Molecular profiling of thyroid nodules on cytologic samples: Findings from an Italian multi-institutional cohort.

[BACKGROUND] Molecular testing is increasingly used to improve preoperative risk assessment of thyroid nodules, especially those with indeterminate cytology. This study evaluated the performance of the Myriapod next-generation sequencing (NGS) DNA-only cancer panel in fine-needle aspiration cytology thyroid samples, correlating findings with postsurgical diagnoses.

[METHODS] A retrospective analysis was performed on fine-needle aspiration cytology specimens from 74 thyroid nodules in the TIR3A, TIR3B, TIR4, and TIR5 categories according to the Italian Consensus for the Classification and Reporting of Thyroid Cytology. DNA from these samples, obtained from residual liquid-based cytology material, was analyzed with the Myriapod NGS panel, targeting 16 genes implicated in thyroid cancer. All patients underwent surgery, allowing for histopathologic correlation.

[RESULTS] The residual liquid-based cytology material yielded adequate DNA for molecular testing in 89.2% of the nodules. All TIR3A (low-risk intermediate) nodules were histologically benign, whereas 50% of TIR3B (high-risk intermediate) nodules were malignant; mutations were identified only in the malignant nodules. In the TIR4 category (suspicious for malignancy), BRAF V600E was the most frequent mutation in malignant nodules. Both TIR5 (malignant) nodules were papillary thyroid carcinomas with a BRAF V600E mutation. The molecular test demonstrated 100% sensitivity, 95.5% specificity, 91.7% positive predictive value, and 100% negative predictive value for samples that were adequate for molecular testing. An intention-to-diagnose analysis that included samples inadequate for molecular testing was also performed, yielding 84.6% sensitivity, 87.5% specificity, 91.7% positive predictive value, and 84% negative predictive value.

[CONCLUSIONS] The Myriapod NGS panel aids in the preoperative assessment of thyroid nodules. Its high negative predictive value may help avoid unnecessary surgery, whereas the detection of specific mutations strongly correlates with malignancy, thus informing surgical planning.