Purpose: High-resolution ultrasound is a safe and costeffective method of identifying and characterizing thyroid nodules, and also for guiding aspiration cytology. But differentiating malignancy from the more frequently occurring benign thyroid nodules has proved challenging as there may be significant overlap in their sonographic appearance. The purpose of this study was to correlate the sonographic characteristics of thyroid nodules with the pathologic results after thyroidecotmy, and to establish the relative importance of these features for predicting the risk for malignancy.
Methods: We reviewed 516 thyroid nodules in 413 patients who underwent thyroidectomy between August 2003 and May 2005, after routine preoperative ultrasound. The following sonographic characteristics of the nodules were evaluated and we determined their sensitivity, specificity and positive predictive value: shape, margin, presence of halo, echo structure, internal echo, echogenicity, calcification and the type of vascularization.
Results: Of the 516 nodules, 327 were malignant nodules and 189 were benign nodules. The nodule size ranged from 5 to 80 mm at the greatest dimension (mean: 20.6 mm). The shape, margin, absence of halo, echo structure, and echogenecity showed statistically significant differences between the benign and malignant nodules in this study. Microcalcifications had low sensitivity but high specificity (13.1% vs 98.9%, respectively). Various combinations of features that have been suggested to be significant predictors of malignancy were also analyzed. The presence of all features was 100% specific for malignancy. According to the receiver operating characteristic curve, the best point for not over-looking malignancy is 2.5. At greater than this point, fine needle aspiration cytology is needed.
Conclusion: This study has shown that ultrasonography is useful for differentiating between benign and malignant thyroid nodules and it can provide the proper indications for aspiration cytology. (J Korean Surg Soc 2006;70:349-356)
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