Ultrasound features and risk stratification systems to identify medullary thyroid carcinoma

Objective: Recently, several scientific societies designed ultrasound (US) risk stratification systems (RSS) to guide the workup of thyroid nodules and decide which nodules should under go fine-needle aspiration cytology (FNAC). However, these systems have been developed against papillary thyroid car cinoma, and scanty data on their role in identifying medullary thyroid carcinoma (MTC) are available. The aims of th is study are to describe the US features of MTC and evaluate the performance of RSS in identifying MTC. Methods: Data of 152 consecutive patients with MTC was evaluated. The re sults of the pre-operative neck US of all patients were collected. Ultrasound features of each MTC were e valuated and classified according to the five main RSS available. Results: Median MTC dimension was 1.3 cm. Most of the nodules showed so lid composition, hypoechoic pattern, and regular margins. About half of them showed the presence of calcifications, but only a subgroup had microcalcifications. A minority of the nodules showed a 'taller than wide' shape. Only 7.9% of all MTC showed the simultaneous presence of at least four US features suggestive o f malignancy. Ultrasonographic high-risk of malignancy of the MTC included in the five RSS, varied from 45.4 to 47.4%, and performing FNAC was suggested in only 48.7 to 63.8% of all MTC. Conclusions: In this series, neither single nor the association of US featu res are specific for MTC. The five main RSS correctly identify less than 50% of MTC and do not suggest perf orming FNAC in about half of them with potentially missed or delayed diagnosis.