RESUMO
BACKGROUND: Thyroid ultrasonography can accurately detect nonpalpable nodules, estimate the size of the nodule during follow-up, and discriminate between solid nodules and simple cysts. Many studies have recently been done to detect malignant thyroid nodules by high-resolution ultrasonography. However, the exact role of high-resolution ultrasonography in distinguishing benign from malignant nodules is still unresolved. We analyzed the sonographic characteristics of thyroid nodules and assessed the diagnostic value of ultrasonography. METHODS: We retrospectively analyzed the sonographic feature of thyroid nodules in patients who had been examined with fine-needle aspiration cytology or had surgery for a thyroid nodule at St. Mary's Hospital, Korea from January 2003 to January 2005. Sonographic features that suggested malignancy include microcalcifications, an irregular or microlobulated margin, marked hypoechogenicity, and a shape that was more tall than it was wide. If even one of these sonographic features was present, the nodule was classified as category 3 (malignant). If a nodule had none of the features described, it was classified as category 2 (benign). Anechogenic cystic nodule was classified as category 1 (benign). RESULTS: Of 124 lesions classified as category 3, 60 were malignant. Of 418 lesions classified as category 1 or 2, 409 was benign. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy based on sonographic classification method were 90%, 86.5%, 48.4%, 97.8%, 86.5%, respectively. CONCLUSIONS: Our results identified sonographic classification with calcification, margin, echogenicity and shape as useful tool in the differentiation of malignant from benign nodule. In view of the high value of negative predictive value of sonographic classification, a more aggressive approach is recommended only for nodules with category 3.
