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Benign thyroid nodules and carcinomas may be distinguished by positron-emission tomography using fluorodeoxyglucose
The background of the study. Positron-emission
imaging with 18-fluorodeoxyglucose (FDG-PET), especially when combined
with computed tomography (FDG-PET/CT), has proven useful in identifying
persistent or recurrent tumor in patients with thyroid carcinoma,
because carcinomas usually take up more FDG than do benign tumors.
This study assessed the value of this test for the preoperative
detection of thyroid carcinoma.
How the study was done. FDG-PET/CT imaging was done in 31 patients, with 48 thyroid nodules, who had been scheduled for surgery. The FDG was given intravenously after the patients had fasted for at least six hours, and the scans were done one hour later. The relative avidity of each nodule for FDG was measured as the standard uptake value (SUV).
The results of the study. Seventeen patients had a solitary nodule, and 14 had multiple nodules. Based on the results of fine-needle-aspiration biopsy, 10 nodules were suspected to be carcinomas, 24 follicular tumors, and 1 benign; 13 were not aspirated. Surgery was done because of the biopsy result in 28 patients, local symptoms in 2, and increasing nodule size in 1.
Among the 48 nodules, 15 were carcinomas and 33 were benign. The carcinomas included 12 papillary carcinomas, 1 Hurthle-cell carcinoma, 1 anaplastic carcinoma, and 1 carcinoma of the kidney that had spread to the thyroid. Among the 33 benign nodules, 13 were follicular adenomas, 8 Hurthle-cell adenomas, and 12 hyperplastic nodules.
The SUV for the 15 carcinomas ranged from 0.0 to 15.5 (mean, 6.5) and the values for the benign nodules ranged from 0.0 to 5.1 (mean, 1.1). The SUV was <5.0 in 30 of the 33 benign nodules (91 percent) and 7 of the 15 carcinomas (47 percent).
The conclusions of the study. In patients with thyroid nodules, FDG-PET/CT imaging can help in distinguishing between benign nodules and carcinomas.
The original article. Mitchell JC, Grant F, Evenson AR, Parker JA, Hasselgren PO, Parangi S. Preoperative evaluation of thyroid nodules with 18-FDG-PET/CT. Surgery 2005;138:1166-75.
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Hurthle-cell carcinomas of the thyroid may have features of
either papillary carcinomas or follicular carcinomas |
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