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 (> or =5 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.