Ultrasonographic characteristics of thyroid nodules - Prediction of malignancy

Background: High-resolution real-time ultrasonography (US) can detect characteristics of thyroid nodules, but the US differentiation between malignant nodules and benign nodules is not well described. Hypothesis: Ultrasonography is useful for predicting malignancy of thyroid nodules. Design: A retrospective study of 329 thyroid nodules (greater than or equal to5 mm) in 309 patients comparing US characteristics and pathological results. Setting: A center for the treatment of thyroid diseases where about 1400 thyroid operations are performed per year. Patients: Between January 1 and June 30, 1999, 309 patients were examined by US before thyroidectomy. Main Outcome Measure: The US characteristics to predict malignancy for both follicular and nonfollicular neoplasms by means of multiple logistic regression analysis. Results: The sensitivity of preoperative US diagnosis was 86.5% for nonfollicular neoplasms and 18.2% for follicular neoplasms. The specificity was 92.3% and 88.7%, respectively. According to multiple logistic regression analysis, margin, shape, echo structure, echogenicity, and calcification were reliable indication of malignancy in nonfollicular neoplasms. According to a receiver operating characteristic curve constructed from this multiple logistic regression analysis, the best point not to overlook malignancy is the point at which sensitivity is 94% and specificity is 87%. The probability of malignancy at this point: is greater than 0.2. For follicular neoplasms, ultrasonographic diagnosis was unreliable, even when multiple logistic regression analysis was applied. Conclusion: We can predict malignancy of nonfollicular neoplasms of the thyroid by using multiple logistic regression analysis based on only 5 features: margin, shape, echo structure, echogenicity, and calcification.