Bilateral Renal Metastasis of Hürthle Cell Thyroid Cancer with Discordant Uptake Between I-131 Sodium Iodide and F-18 FDG / 대한핵의학회잡지

Renal metastasis of thyroid cancer is extremely rare. We report the case of a 62-year-old woman with Hürthle cell thyroid cancer (HCTC) with lungs, bones, and bilateral kidneys metastases. The renal metastatic lesions were clearly demonstrated by ¹³¹I whole body scan (WBS) with SPECT/CT. However, they exhibited false-negative results in ¹⁸F-FDG PET/CT, kidney ultrasonography, and contrast-enhanced CT scan. The findings imply that tumors have low glucose metabolism and are able to accumulate radioiodine, which is not commonly found in the relatively aggressive nature of HCTC. The patient received two sessions of 200 mCi ¹³¹I therapy within 6 months duration. There was complete treatment response as evaluated by the second post-therapeutic ¹³¹I SPECT/CT and serum thyroglobulin. To our knowledge, renal metastasis from HCTC with positive ¹³¹I but negative ¹⁸F-FDGuptake has not been reported in the literature. This case suggests that ¹³¹I SPECT/CTis useful for lesion localization and prediction of ¹³¹I therapy response.

The Value of FDG-PET in Reoperation of the Recurrent Papillary Thyroid Carcinoma with Elevated Thyroglobulin Levels and Negative I131 WBS

PURPOSE: We evaluated the diagnostic accuracy and useful ness of FDG-PET to determine the proper extent of surgery in recurrent papillary thyroid cancer patients with elevated thyroglobulin levels and negative I131 WBS. METHODS: FDG-PET was performed in 16 recurrent papillary thyroid cancer patients with elevated thyroglobulin levels and negative I131 WBS. In 9 patients, FDG-PET was performed to localize the recurrent lesions. In 7 patients, the recurrent lesions were initially diagnosed by physical examination or other image studies and the FDG-PET was subsequently performed to detect additional recurrent lesions. All suspected lesions detected by FDG-PET and other studies were explored. RESULTS: Among the 9 patients in whom FDG-PET was performed to localize the recurrent lesions, the recurrent lesions were detected only by FDG-PET in 4 patients. Among the 7 patients in whom FDG-PET was performed additionally to detect additional recurrent lesions, another recurrent cervical regions were detected by FDG-PET in 2 patients. However, the same lesions were able to be identified by ultrasonography. A total of 26 cervical regions were explored in 16 patients. There were 4 FDG-PET false positive regions and 2 FDG-PET false negative regions. Unnecessary surgery was performed in 4 cervical regions in 4 patients. CONCLUSION: FDG-PET was very useful in detecting small early recurrent lesions but was unable to contribute to the detection of additional recurrent cervical regions in the pa-tients in which the recurrent lesion had already been by physical examination or other studies. Other image studies are necessary to supplement the FDG-PET in false positive or false negative cases.