Sonographic differentiation of partially cystic thyroid nodules: a prospective study

Abstract

Background and purpose: There is no prospective study related to the sonographic differentiation of malignant PCTN from benign PCTN. This prospective study was designed to evaluate differentiation of benign from malignant PCTNs with thyroid sonography.

Materials and methods: Two hundred thirteen PCTNs in 196 patients who had consecutively undergone prospective sonographic diagnosis and US-FNAB were included. The PCTNs were evaluated according to their configuration and the presence of calcification, a free margin, vascularity, spongiform appearance or daughter cysts, colloid crystal, nodule shape, and echogenicity. Each PCTN was prospectively classified into 1 of 4 diagnostic categories: benign features, probably benign, suspicious for malignancy, and malignant features. We calculated the diagnostic efficacy of a prospective sonographic diagnosis for PCTNs by comparing it with cytopathologic results.

Results: Among the 213 PCTNs, 53 underwent thyroid surgery. The sonographic classifications for 213 PCTNs included benign features (n = 182), probably benign (n = 19), suspicious for malignancy (n = 7), and malignant features (n = 5). When nonsurgical PCTNs (n = 160) with benign sonographic findings and benign cytology were considered negative, the sensitivity, specificity, PPV, NPV, and accuracy of the prospective diagnosis of PCTNs were 72.7%, 98.0%, 66.7%, 98.5%, and 96.7%, respectively. On the basis of individual analysis, eccentric configuration with an acute angle and microcalcifications were significantly associated with malignancy, but a concentric configuration, a smooth free margin, peripheral vascularity, spongiform appearance or daughter cysts, and intranodular colloid crystals showed a statistically significant association with benignity.

Conclusions: Our prospective sonographic diagnoses of PCTNs, especially those >2 cm, were highly reliable.

Fig 1.

The 4 categories of thyroid sonography for the classification of PCTNs. A, Benign features in a 60-year-old woman. A longitudinal sonogram of nodular hyperplasia in the left lobe shows a concentric configuration with a centrally located cystic component, a smooth free margin, an ovoid shape, and isoechogenicity. B, Probably benign in a 50-year-old woman. A transverse sonogram of nodular hyperplasia in the left lobe shows an eccentric configuration with a blunt angle between the solid component and the wall (arrows), a smooth free margin, and isoechogenicity. C, Suspicious for malignancy in a 28-year-old woman. A longitudinal sonogram of a papillary thyroid carcinoma in the left lobe shows an eccentric configuration with an acute angle between the solid component and the wall (arrows), a microlobulation, and isoechogenicity. D, Malignant features in a 45-year-old woman. A longitudinal sonogram of a papillary thyroid carcinoma in the left lobe shows an eccentric configuration with an acute angle (arrows), macrolobulation, microcalcifications, and hypoechogenicity.

Fig 2.

A PCTN assigned to the suspicious for malignancy category on thyroid sonography in a 29-year-old man (a false-positive). A and B, Transverse and longitudinal sonograms of a PCTN in the left midlobe show an eccentric configuration with an acute angle (arrows), a smooth free margin, an ovoid shape, and isoechogenicity. The lesion was surgically confirmed as nodular hyperplasia at the patient's request despite benign cytology on the US-FNAB (1.2 × 1.6 × 1.9 cm).