Ultrasonographic characteristics of thyroid nodules: prediction of malignancy

Abstract

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.