Should we use ultrasound features associated with papillary thyroid cancer in diagnosing medullary thyroid cancer?

In thyroid nodule management, ultrasound (US) features, such as hypoechogenicity of the lesion, irregular margins, microcalcifications, and intralesional vascular signal, alone or combined, have to be considered as suggestive for malignancy. Because of the low prevalence of medullary thyroid cancer (MTC), a few papers analyzed US characteristics associated with this cancer in small series, with controversial results. Aim of this study was to evaluate in MTC the US risk factors of thyroid nodule. In this order, a series of nodules histologically proven as MTC and a group of nodules with histology of papillary cancer (PTC) were retrospectively compared with a control group of benign nodule. Fifty percent MTC were solid hypoechoic and 16% showed microcalcifications with significant difference with respect to the benign group (p<0.05 for both parameters), while no significant difference was recorded regarding margins nor nodular vascularization. The presence of at least one US risk feature was almost equal in MTC (58.3%) and controls (55.5%). On the contrary, at least one US risk factor was significantly (p<0.001) more frequent in PTC than in benign group or MTC series. This study showed low frequency of ultrasound features associated to PTC when analyzed in medullary cancer. Because of the poor literature focusing on this topic, and the herein used design, these data contribute to the knowledge about presentation of MTC at US. We advice for further prospective studies on larger series to define the US presentation of this cancer type.