Accuracy of FDG-PET Scanning to Diagnose Malignant Thyroid Nodules

Inclusion Criteria: * Documented history of a solitary thyroid nodule or a dominant nodule within multinodular disease, with fine needle aspiration demonstrating a follicular or indeterminate cytologic examination. If a core needle biopsy was performed instead of a fine needle aspiration, demonstrating follicular or indeterminate cytology, the patient is eligible if the biopsy procedure was felt to be minimally disruptive to the nodule architecture, based on a review by the PI or nuclear medicine investigator. * Thyroid nodule must be palpable on physical examination or have a minimum size of 1 cm in diameter by ultrasonography, CT or MRI. The minimum size criterion was established to address the spatial resolution limitations of PET/CT imaging. * Scheduled for surgical excision of thyroid nodules within 3 months of the date of the FDG-PET/CT scan. * Ability to tolerate lying supine for a FDG-PET/CT examination. * Age \>/= 18 and \</= 105 (This disease is rare in children and therefore the study will be limited to adults.) * Willing to participate in all aspects of the study (patient may opt out of the tissue collection portion.) * Patient must be euthyroid with a serum TSH or a free T4 level within the institutional upper and lower limits of normal, measured within 6 months of registration. NOTE: mild deviations from the institutional normal limits may be considered acceptable if the patient has achieved a clinically euthyroid state with medication at a stable dose for \>3 months, and the TSH is considered to be at target by the patient's treating physician. In patients with hyperthyroidism requiring treatment, this euthyroid state may be achieved with administration of a thionamide such as propylthiouracil prior to FDG-PET/CT exam. Patients with hyperthyroid inflammatory conditions such as thyroiditis and toxic multinodular goiter often exhibit increased glucose uptake resulting in diffuse uptake of FDG which may obscure visualization of a thyroid tumor. * If female, patient must have a negative pregnancy test at the time of registration, be post-menopausal (with no period in the last twelve months), have had a tubal ligation at least twelve months ago, or have had a hysterectomy. * In patients with multinodular disease and a dominant nodule, the nuclear medicine physician responsible for FDG-PET/CT scan interpretation must determine whether the indeterminate nodule can be discriminated on FDG-PET/CT imaging prior to enrollment. * A signed and dated written informed consent obtained from the patient or the patient's legally acceptable representative prior to study participation. Exclusion Criteria: * Patient has a fasting glucose level \> 200 mg/dL at the time of the PET/CT scan * Patient has had prior neck surgery or radiation that in the opinion of the investigator has disrupted tissue architecture of the thyroid * Patient has evidence of infection localized to the neck in the 14 days prior to the FDG-PET/CCT scan * Patient does not meet any of the inclusion criteria