Objective: When a fine needle aspiration biopsy of a thyroid nodule suggests follicular neoplasm, surgery is required for diagnosis. Establishing the diagnosis preoperatively would allow the patient to undergo the appropriate initial thyroidectomy. Preoperative [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging may be able to determine malignancy in follicular neoplasms. Study Design: Prospective cases series. Subjects and Methods: Twenty-three patients with a diagnosis of follicular neoplasm underwent presurgical FDG-PET at 60, 90, and 120 minutes after injection of fluorodeoxyglucose (F18). Thyroidectomy was performed with comparison of the histopathologic results with the FDG-PET results. Results: There were 5 malignant conditions and 18 benign conditions identified with the standard uptake valve (SUV) ranging from 0.9 to 44.8. The follicular thyroid cancers that exhibited only capsular invasion had an average SUV of 3.1, whereas those with vascular invasion had an average SUV of 39.9. The SUV increased in 80% of the malignant cases but in only 50% of the benign cases. Conclusion: Despite certain patterns being suggestive of malignancy, FDG-PET can not consistently predict the malignant potential of a follicular neoplasm.
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