The predictive value of ultrasound findings in the management of thyroid nodules

Background: Thyroid nodules are a common medical problem, but whether fine-needle aspiration cytology (FNAC) is mandated for smaller non-palpable nodules, is controversial. Aim: To evaluate whether ultrasonographic features of thyroid nodules are associated with histological malignancy, and to identify useful criteria for clinical decision-making. Design: Prospective observational study. Methods: From January 1991 to September 2004, 5198 patients were referred to our hospital for ultrasound evaluation of thyroid nodules. Overall, 7455 nodules (diameters from 6 to 100 mm) were examined; 2865 (38.4%) were < 10 mm in diameter. All patients with suspicious or malignant cytology underwent surgery. Results: Of the 349 nodules undergoing surgery, 284 were malignant. The prevalence of cancer was slightly higher in nodules >= 10 mm in diameter vs. those < 10 mm (5.5% vs. 3.0%, p < 0.01). However, histological type and local aggressiveness were largely independent of nodule size. Microcalcifications (72.2% vs. 28.7%; p < 0.001; OR 6.4, 95%CI 4.9-8.4), blurred margins (52.8% vs. 18.8%; p < 0.001; OR 4.8, 95%CI 3.8-6.1), solid hypoechoic appearance (80.6% vs. 52.4%; p < 0.001; OR 3.8, 95%CI 2.8-5.1), size >= 10 mm (77.4% vs. 64.9%; p < 0.001; OR 1.9, 95%CI 1.4-2.5) and intranodular vascular pattern type 2 (61.6% vs. 49.7%; p < 0.001; OR 1.6, 95%CI 1.2-2.0) were all significantly more frequent in malignant than in benign nodules. These associations were similar when large and small nodules were analysed separately. Discussion: No single parameter, including nodule size, satisfactorily identifies a subset of patients to be electively investigated by FNAC, although several may be useful in this regard.