Incidence of Incidental Thyroid Nodules on Computed Tomography (CT) Scan of the Chest Performed for Reasons other than Thyroid Disease

Previous studies demonstrate an approximately 16% incidence of incidental thyroid nodules (ITNs) on Computed To-mography (CT) of the head/neck and thorax combined. Malignant disease is present in many cases. No study to date has quantified ITNs on CT of the thorax alone, an examination performed more frequently than head/neck CT. Our objective was to determine the prevalence and significance of ITNs with further stratification based on size criteria of non-dominant (<10 mm) and dominant ( >10 mm) on CT imaging of the chest performed for indications other than thyroid disease and to assess if these were further evaluated. A retrospective analysisof 500 patients (257 men and 243 women; mean age, 58.3 +/– 16.7 years) with thoracic CT scans performed at Erlanger Health System from October 2007 to October 2008 was performed. ITNs were noted in 61 (12.2%) of patients. Nodules were solitary in 43 patients (70.5%) and multiple in 18 (29.5%). Thirty-three patients (6.6%) were found to have a dominant nodule >10 mm. Sixteen of the 33 patients with dominant nodules received further workup showing benign pathology in 50%. More than 50% of the 33 dominant nodules received no follow-up at all. Chest CT demonstrates many ITNs. The incidence in this study was 12.2% with 6.6% being potentially malignant dominant thyroid nodules. Partial thyroid glands were visualized in 58.2% exams, implying an incidence of 12.2% ITNs is an underestimate. It may be beneficial for routine chest CT to be extended 2cm superiorly in order to ensure full visualization of the thyroid gland and related pathology.