A 63 year old male who underwent total thyroidectomy for papillary thyroid carcinoma received 150 mCi of I-131 for remnant ablation, seen on whole body scan as two foci of iodine uptake in the anterior neck. He was found to have high serum thyroglobulin levels (107 mg/ml) on surveillance but the whole body I-131 scan (below) was negative for iodine avid recurrence or metastasis.

Whole body FDG PET-CT demonstrated hypermetabolic level IIb and level III lymphadenopathy. Right neck dissection was performed and out of the 15 nodes removed, four of were found to have metastatic papillary carcinoma. This case demonstrates the usefulness of PET-CT in detecting iodine negative but FDG avid metastatic thyroid carcinoma after total thyroidectomy.

1. Chung JK, So Y, Lee JS, Choi CW, Lim SM, Lee DS, Hong SW, Youn YK, Lee MC, Cho BY. Value of FDG PET in papillary thyroid carcinoma with negative 131I whole-body scan. J Nucl Med. 1999 Jun;40(6):986-92.

2. Palmedo H, Bucerius J, Joe A, Strunk H, Hortling N, Meyka S, Roedel R, Wolff M, Wardelmann E, Biersack HJ, Jaeger U. Integrated PET/CT in differentiated thyroid cancer: diagnostic accuracy and impact on patient management. J Nucl Med. 2006 Apr;47(4):616-24.

3. Finkelstein SE, Grigsby PW, Siegel BA, Dehdashti F, Moley JF, Hall BL. Combined [18F]Fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) for detection of recurrent, 131I-negative thyroid cancer. Ann Surg Oncol. 2008 Jan;15(1):286-92.

This case was compiled by Dr. David He, BCM