Benign and Malignant Thyroid Incidentalomas Are Rare in Routine Clinical Practice: A Review of 97,908 Imaging Studies

Thyroid nodules incidentally identified on imaging are thought to contribute to the increasing incidence of thyroid cancer. We aim to determine the true rate of incidental thyroid nodule reporting, malignancy rates of these nodules, and to compare these findings with rates of detection by dedicated radiology review.

A cross-sectional analysis was done to determine the prevalence of thyroid nodules in radiologist reports by analyzing all reports for CT, PET, and MRI scans of the head, neck, and chest as well as neck ultrasounds performed at a tertiary care center from 2007 to 2012. Retrospective chart review was performed on patients with a reported thyroid nodule to determine clinical outcomes of these nodules. Radiology reports were compared with dedicated radiology review of 500 randomly selected CT scans from the study group to determine the difference between clinical reporting and actual prevalence of thyroid nodules.

97,908 imaging studies met inclusion criteria, and 387 (0.4%) thyroid incidentalomas were identified on radiology report. One hundred and sixty three (42.1%) of these nodules were worked up with fine-needle aspiration, diagnosing 27 thyroid cancers (0.03% of all studies, 7.0% of reported incidentalomas). The prevalence of incidentalomas clinically reported was 142/100,000 CT scans, 638/100,000 MRIs, 358/100,000 PET scans, and 6,594/100,000 ultrasounds. In contrast, review of CT scans screening for thyroid nodules had a prevalence of 10%.

Routine clinical reporting of incidental thyroid nodules is far less common than on dedicated review.

These data contradict the notion that incidentalomas contribute significantly to rising thyroid cancer rates.