Focal thyroid FDG-PET incidentaloma

Occasionally, a patient may be referred for an incidental thyroid nodule noted only on 18-fluorodeoxyglu-cose positron-emission tomography (FDG-PET) scan obtained for another purpose, usually evaluation of another known or suspected malignancy.

Among a group of 32 patients with a focal thyroid FDG-PET incidentaloma who then underwent FNAB, 16 (50%) were found to be malignant — 14 were papillary thyroid carcinoma and 2 were metastatic from breast and esophagus.^[61]

Thus, thyroid incidentalomas identified on FDG-PET scan have a high risk of malignancy and thus should be evaluated further, starting with FNAB.

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SURGERY: Volume 138, Issue 6, Pages 1166-1175 (December 2005)

Fifteen of 48 lesions were malignant and 33 were benign. Nine of 15 malignant lesions were 18FDG-avid (sensitivity 60%). Thirty of 33 benign lesions were 18FDG-cold (specificity 91%). Positive and negative predictive values were 75% and 83%, respectively.

^{18FDG-PET/CT provides a high negative predictive value for malignancy, making this a potentially useful tool in the evaluation of thyroid nodules with indeterminate fine-needle aspiration. However further studies with larger sample sizes are needed to determine the true efficacy of this test.}