Thyroid incidentalomas: epidemiology, risk stratification with ultrasound and workup

A thyroid incidentaloma is an unexpected, asymptomatic thyroid tumor fortuitously discovered during the investigation of an unrelated condition. The prevalence rate is 67% with ultrasonography (US) imaging, 15% with computed tomography (CT) or magnetic resonance imaging (MRI) of the neck, and 1-2% with fluorodeoxyglucose (FDG) positron emission tomography. In the absence of a history of external beam radiation or familial medullary thyroid cancer, the risk of malignancy ranges between 5 and 13% when discovered with US, CT or MRI, but is much higher if based on focal FDG uptake (30%). All patients with a thyroid incidentaloma, independent of the mode of detection, should undergo a dedicated neck US with risk stratification: US imaging allows a quantitative risk stratification of malignancy in thyroid nodules, named 'reporting system' or 'TIRADs' (thyroid imaging reporting and data system). The reported sensitivity ranges from 87 to 95% for the detection of carcinomas and the negative predictive value from 88 to 99.8%. We suggest that the indications for fine-needle aspiration be based mainly on size and US risk stratification. However, the diagnosis and workup of thyroid incidentalomas leads to superfluous surgery for benign conditions, and excess diagnosis and treatment of papillary microcarcinomas, the vast majority of which would cause no harm. Recognizing this must form the basis of any decision as to supplementary investigations and whether to offer therapy, in a close dialogue between patient and physician. The current use of minimally invasive nonsurgical ablation options, as alternatives to surgery, is highlighted.