Imaging of medullary thyroid carcinoma

Abstract

About 10% of thyroid cancers are medullary thyroid carcinoma (MTC) and can occur sporadically, familially and in the context of typeII multiple endocrine neoplasia (MEN). Imaging plays apivotal role in screening family members and in diagnosis. Diagnosis is based on ultrasound (US), thyroid scintigraphy, serum calcitonin and carcinoembryonic antigen (CEA) as well as fine needle biopsy. High-resolution US is the most important imaging method for locoregional staging, combined with computed tomography (CT) of the mediastinum. Positron emission tomography (PET-CT) using 18-F-DOPA is particularly suited for suspected occult metastases in case of rising tumor markers in serum. Diagnosis is made based on cytologic findings in ahypoechoic, cold thyroid nodule, combined with an elevation of serum calcitonin and CEA. US is the most important imaging modality during routine follow-up. CT is indicated for suspected mediastinal, lung, or liver metastases. CT should be replaced by MRI as early as possible to prevent significant cumulative radiation doses over time. Although MTC is curable by surgery only, owing to its radio- and chemoresistance, the disease will often progress only slowly, and even patients with metastases will frequently survive 10years or longer. For more aggressive variants and late symptomatic stages, targeted drugs that have the potential to indicate stabilization or even apartial remission of the disease are under clinical investigation or already approved.