Utility of elastography for differential diagnosis of benign and malignant thyroid nodules.

OBJECTIVE: 1) To classify the appearance of thyroid nodules displayed on ultrasound elastography; 2) to explore the sensitivity and specificity of this examination for differentiating benign and malignant nodules, with histopathologic analysis as the reference standard; and 3) to evaluate its utility for avoiding unnecessary procedures.

STUDY DESIGN: Diagnostic test assessment.

SETTING: Community hospital.

SUBJECTS AND METHODS: Forty-seven thyroid nodules in 44 consecutive patients were examined with ultrasound elastography. The images we obtained were classified into four patterns. In addition, the mean strain index of the thyroid nodule and that of the sternocleidomastoid muscle were measured, and the nodule-to-muscle strain ratio was calculated. As the reference findings, the presence or absence of calcification, irregular margins, and hypoechogenicity of the thyroid nodules were examined using B-mode ultrasound.

RESULTS: Elastography patterns 3 and 4 were predictive of malignancy, with 73 percent sensitivity (95% confidence interval [CI]: 39%-94%) and 64 percent specificity (95% CI: 46%-79%). Additionally, all nodules without calcification and those that presented with patterns 1 or 2 were benign. A strain ratio greater than 1.5 was set as the predictor of thyroid malignancy. This criterion showed 90 percent sensitivity (95% CI: 59%-100%) and 50 percent specificity (95% CI: 33%-67%).

CONCLUSION: Although elastography can assist in the differential diagnosis of thyroid nodules, its diagnostic performance is not ideal at present. Further improvements in the technique and the diagnostic criteria are necessary for this examination to provide a useful contribution to diagnosis.