18F-FDG PET and (superscript 99m)Tc-MDP Bone Scintigraphy in the Detection of Bony Metastasis from Medullary Thyroid Cancer: A Case Report

A 52-year-old man with history of medullary thyroid cancer (MTC) received total thyroidectomy and left neck lymph node dissection six years ago and then received wide excision for right chest wall metastases one month later. After operation, he received (superscript 99m)Tc-MDP bone scintigraphy and 18F-fluorodeoxyglucose positron emission tomography (FDG PET) for follow up. The bone scintigraphy revealed only a limited number of metastatic bony lesions. However, in contrast with bone scintigraphy, FDG PET showed wide-spread multiple metastatic bony lesions, much more than that shown by bone scintigraphy. The difference of imaging mechanism and morphologic characteristics of bony metastasis from MTC might attribute to the discrepancy in diagnostic sensitivity in MTC with bone metastasis between FDG PET and bone scintigraphy. As compared with bone scintigraphy, FDG-PET scan showed higher sensitivity for the detection of bony metastasis from medullary thyroid cancer.