Medullary Thyroid Carcinoma: Imaging

Imaging plays an important role in early detection and staging of medullary thyroid carcinoma (MTC) as well as in follow-up to localize early recurrence. MTC is a rare, calcitonin-secreting thyroid malignancy often diagnosed by ultrasound and calcitonin screening as part of the routine workup for any thyroid nodule. If calcitonin is elevated, imaging studies are needed for preoperative staging, which dictates surgical management. This can be done by ultrasound of the neck and abdomen. Computed tomography (CT) or magnetic resonance imaging (MRI) studies for more distant disease are done preoperatively if calcitonin levels are higher than 500 pg/ml. Neither FDG-PET/CT nor F-DOPA-PET/CT are used routinely for preoperative staging but may contribute in doubtful individual cases. Postoperative elevated calcitonin is related to persistence or recurrence of MTC. Imaging studies to localize tumor tissue during postoperative follow-up include ultrasound, CT, MRI as well as PET studies. They should be used wisely, however, since treatment consequences are often limited, and even patients with persistent disease may survive long enough to accumulate significant radiation doses. Imaging studies are also useful for diagnosis of associated components of the hereditary MTC such as pheochromocytoma and primary hyperparathyroidism (pHPT).