Diagnostic accuracy of thyroid nodules with indeterminate cytology when combined with ultrasonographic risk

To evaluate the added diagnostic value of ultrasonographic risk levels to cytological diagnoses in nodules with Bethesda III and IV cytology.

This retrospective study was conducted in Jeddah, Saudi Arabia, and involved analyzing thyroid nodules from patients who underwent thyroidectomy between 2016 and 2023. We focused on pathology, US risk stratification based on the 2015 American Thyroid Association (ATA) guidelines, and fine-needle aspiration cytology (FNAC) using the Bethesda system. We calculated malignancy rates for each ultrasound (US) and FNAC category, with the indeterminate cytology groups defined as follicular lesions of undetermined significance (FLUS) and follicular neoplasms (FN).

In 290 patients, malignancy rates in the high-risk US group were 72%. In patients with FLUS, the malignancy rate was 36.9%, while in those with FN, it was 50%. For FLUS and FN, high-risk US features showed a sensitivity of 47%, a specificity of 81%, and a kappa of 29%. Combining FLUS with high-risk US features improved sensitivity to 50%, specificity to 80%, and kappa to 32%.

For indeterminate thyroid cytology, US features can guide decision-making, supporting surgery in patients with high-risk US findings rather than follow-up or repeat FNAC.