US-elastography in the differential diagnosis of benign and malignant thyroid nodules

Ultrasound (US)-elastography is a newly developed imaging technique for the reconstruction of tissue stiffness by measuring the degree of tissue's deformation in response to the application of an external force. This technique has previously been shown to be useful in the differential diagnosis between benign and malignant tumors.

The objective of this study was to assess the diagnostic accuracy of US-elastography in the differential diagnosis of thyroid cancer, using the cytologic/histopathologic analysis as the reference standard. A total of 67 consecutive patients with thyroid nodules who were referred to the Thyroid Unit at the Policlinico MultiMedica were enrolled in this prospective study between January and December 2006. Eighty-six nodules in these patients were examined by US B-mode, US color-power-Doppler, and US-elastography. Nodules were subjected to fine-needle aspiration biopsy and patients with a reading of malignant or indeterminate had thyroid surgery. The final diagnosis was based on the cytology reading in those who did not have surgery and the histopathology reading in those who had surgery. US-elastography scores were based on four classes of tissue stiffness (class 1 for soft nodules; class 2 and 3 for nodules with an intermediate degree of stiffness; class 4 for anelastic lesions).

Seventeen nodules were malignant and 69 were benign. Sensitivity and specificity of the US-elastography for thyroid cancer diagnosis were 94.1% (16/17) and 81% (56/69), respectively. The positive and negative predictive values were 55.2% (16/29) and 98.2% (56/57), respectively. The accuracy of the technique was 83.7%.

US-elastography is a promising technique that, combined with other US modalities, is easy and rapid to perform and can help to identify thyroid nodules that are likely to be malignant. An important limitation is probably lack of sensitivity for follicular thyroid carcinoma.