Ultrasound-Based Diagnosis for Solid Thyroid Nodules with the Largest Diameter <5 mm

This study was aimed at assessing the efficacy of using an ultrasound (US)-based classification system to diagnose solid thyroid nodules with the largest diameter <5 mm (i.e., small solid nodules). For 406 small solid nodules in 365 patients who underwent thyroid US and US-guided fine-needle aspiration, each thyroid nodule was prospectively classified into one of five diagnostic categories: benign, probably benign, borderline, possibly malignant and malignant. Of 406 nodules, 145 were surgically removed: 95 papillary thyroid carcinomas, 1 follicular thyroid carcinoma, 1 poorly differentiated carcinoma, 3 pseudonodules related to thyroiditis and 45 nodular hyperplasias. On the basis of the histopathologic results, the diagnostic accuracies of US diagnosis and cytologic diagnosis were similar, but the sensitivity of US diagnosis was higher than that of cytologic diagnosis, and the specificity and positive predictive values of US diagnosis were lower those of cytologic diagnosis. An US-based classification system may be helpful for the diagnosis and management of small solid nodules.