Thyroid follicular neoplasms: Can sonography distinguish between adenomas and carcinomas?

Purpose. The purpose of this study was to determine whether sonography (US) can usefully differentiate thyroid follicular adenoma (FA) and follicular carcinoma (FC). Methods. This retrospective study included 60 pathologically proven FAs and 66 FCs in 123 consecutive patients (17 males and 106 females) with a mean age of 47 ± 13 years, (17-73 years) who underwent thyroid surgery. We analyzed US features of each nodule, including maximum diameter, echogenicity, composition, presence of calcification, margins, and presence of halo. The frequencies of each US feature were compared by using the χ² test or Fisher's exact test between FAs and FCs. The relative risk of malignancy was evaluated by logistic regression analysis. Results. Isohypoechoic echogenicity, predominantly solid or mixed echotexture, and presence of microcalcifications or rim calcifications were associated with FC (p < 0.05). Logistic regression analysis demonstrated that predominantly solid or mixed echotexture and microcalcifications or rim calcifications were associated with significant increases in relative risk for FC (odds ratio 8.1 and odds ratio 13.5, respectively, p < 0.01). Conclusions. The US features of isohypoechoic echogenicity, predominantly solid or mixed echotexture, and microcalcifications or rim calcifications are more common in FC than in FA.