What is the significance of a hot thyroid nodule incidentally discovered on positron emission tomography (PET)?
Fluorodeoxyglucose (FDG) whole-body PET scan is commonly used in the evaluation and surveillance of patients with various types of cancer. A focal area of increased FDG uptake within the thyroid is incidentally noted in up to 4% of PET scans. The risk of malignancy in these lesions is about 33%. Thus, thyroid incidentalomas noted on PET scans have a high risk of malignancy and warrant appropriate diagnostic evaluation. Diffuse FDG uptake is usually related to underlying thyroiditis and, in most cases, is not indicative of malignancy.