Usefulness of [99mTC]MIBI and [18F]fluorodeoxyglucose for imaging recurrent medullary thyroid cancer and hyperparathyroidism in MEN 2a syndrome.

We report the case of a MEN 2a patient with a history of medullary thyroid cancer (MTC) treated by total thyroidectomy, who presented an increasing calcitonin level, suggesting tumor recurrence. Conventional radiographic and radionuclide imaging failed to localize the responsible lesions. A planar and tomographic (SPECT) [99mTc]MIBI scan, performed in order to investigate a recent hyperparathyroidism localized a parathyroid adenoma and revealed an abnormal uptake in the left lateral neck region, corresponding to apparently banal lymph nodes on MRI. This abnormal uptake was also observed on a [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) study and was proven to be an uptake in MTC lymph nodes metastases as confirmed by histopathologic analysis. We conclude that, using an adequate acquisition protocol (i.e. SPECT), [99mTc]MIBI scan is potentially able to localize both parathyroid adenoma and recurrent MTC at one and the same time, particularly in case of non-diagnostic conventional imaging techniques. In this setting, the potential usefulness of FDG-PET is also discussed.