Medullary Thyroid Carcinoma: Comparison With Papillary Thyroid Carcinoma and Application of Current Sonographic Criteria

The aim of this study was to evaluate whether sonography can diagnose medullary thyroid carcinoma (MTC) as a malignant lesion using widely accepted sonographic criteria and to compare which sonographic findings of MTC are different from findings for papillary thyroid carcinoma (PTC).The study included 42 patients (13 men and 29 women; mean age, 48 years) with 46 MTCs and 51 consecutive patients (10 men and 41 women; mean age, 48 years) with 55 PTCs that were confirmed at surgery. Two radiologists retrospectively determined the sonographic diagnoses according to malignant criteria (a taller-than-wide shape, spiculated margin, marked hypoechogenicity, and microcalcifications or macrocalcifications) and compared the sonographic findings of MTCs and PTCs.MTCs were diagnosed as malignant for 72% of cases by sonography, whereas PTCs were 87% malignant (p = 0.0511). Compared with PTCs, MTCs were larger (mean size, 2.3 +/- 1.5 cm vs 1.1 +/- 1.1 cm) (p = 0.001; odds ratio [OR], 3.84; 95% CI, 1.719-8.565), more frequently showed the presence of a cystic change (33% vs 4%) (p = 0.0226; OR, 0.10; 95% CI, 0.014-0.725), and more commonly showed homogeneous echotexture of the solid portion (59% vs 31%) (p = 0.0004; OR, 0.08; 95% CI, 0.019-0.321). MTCs tended to show an oval shape and circumscribed margin, but there was no statistical significance in multivariate analysis. There were no significant differences in echogenicity, presence, and type of calcification for MTCs and PTCs.Currently accepted sonographic criteria can be applied for a diagnosis of MTCs. MTCs differ from PTCs in size, presence of a cystic change, and echotexture.