Can Pathology of a Thyroid Nodule Be Determined by Positron Emission Tomography?

Abstract

Objective: Positron emission tomography (PET) uptake in the thyroid gland is common. It occurs incidentally in diagnosis or surveillance of many cancers. Focal uptake indicates thyroid mass lesions. The goal was to determine if standardized uptake values (SUV) on PET can predict pathology in masses of the thyroid gland. Method: A total of 23,982 PET scans were retrospectively reviewed from the University of Arkansas for Medical Sciences in Little Rock, AR. These scans were performed from 2002 to 2010. 1,290 (5.4%) of scans had uptake in the thyroid gland, 614 were considered to be diffuse and 676 were considered focal. Results: A total of 112 patients had PET scan with accompanying thyroid cytology or pathology. The mean SUV for benign (N = 78) was 3.75 ± 2.99 and for malignant (N = 35) was 8.22 ± 7.91, × 2 0.0011. Age, lesion size, and gender were not significant. Receiver operating curves (ROC) were constructed with empirical or binormal distribution assumptions. The area under the curve (AUC) was 0.693 and 0.702 respectively. A SUV of 3.6 maximized empirical sensitivity and sensitivity while minimizing (FP) and negatives (FN). A SUV threshold of 3.6 minimized binormal FP and FN whereas a SUV of 7.9 maximized sensitivity and specificity. Conclusion: Uptake on the thyroid on PET scan is a common incidental finding. The above data can help inform providers as to when these incidental lesions need to be aggressively evaluated through ultrasound guided needle biopsy or excision or when they can be observed.