The value of quantifying 18F-FDG uptake in thyroid nodules found incidentally on whole-body PET-CT

Objective To determine if quantification of [F-18]fluorodeoxyglucose (F-18-FDG) uptake in a thyroid nodule found incidentally on whole-body F-18+DG positron emission tomography-computed tomography (PET-CT) can be used to discriminate between malignant and benign aetiology. Methods A retrospective review of all patients with focally high uptake in the thyroid as an incidental finding on F-18-FDG PET-CT from May 2003 through May 2006. The uptake in the nodules was quantified using the maximum standardized uptake value (SUVmax). The aetiology was determined by cytology and/or ultrasound, or on histopathology. Results Incidental focally high uptake was found in 79/7347 patients (1.1%). In 31/48 patients with adequate follow-up, a benign aetiology was determined. Median SUVmax for the benign group was 5.6, range 2.5-53. Malignancy was confirmed in 15/48 patients. The malignancies were papillary thyroid carcinoma in 12, metastasis from squamous cell carcinoma in one, and lymphoma in two. Median SUVmax for the malignant lesions was 6.4, range 3.5-16. Cytology suspicious for follicular carcinoma was found in 2/48 patients. No statistical difference (P=0.12) was found among the SUVmax between the benign and malignant groups. Conclusion Focally high uptake of F-18-FDG in the thyroid as an incidental finding occurred in 1.1% of the patients. Malignancy was confirmed or was suspicious in 17/48 (35%) of the patients that had adequate follow-up. There was no significant difference in the SUVmax between benign and malignant nodules. Nucl Med Commun 28:373-381 (c) 2007 Lippincott Williams & Wilkins.