Compressibility of Thyroid Masses: A Sonographic Sign Differentiating Benign From Malignant Lesions?

OBJECTIVE. The purpose of this study was to assess the manual compressibility of thyroid masses with an ultrasound probe and to determine whether this ultrasound feature can be used to differentiate benign from malignant thyroid lesions. SUBJECTS AND METHODS. We prospectively compared images obtained during compression with an ultrasound probe and noncompressed ultrasound images of 180 pathologically proven thyroid masses (51 malignant, 129 benign) smaller than 2 cm in 169 patients (127 women, 42 men; mean age, 51.2 years). The size (anteroposterior and transverse dimensions) and shape (ratio of anteroposterior to transverse dimension) of the selected lesions were measured on both noncompressed and compressed ultrasound images at a computer workstation, and the compressibility (anteroposterior-to-transverse ratio on noncompressed images minus anteroposterior-to-transverse ratio on compressed images) was calculated. Compressibility was analyzed to determine its association with histopathologic results (benign versus malignant) and the characteristics of the thyroid mass (involved lobe, location in lobe, halo, and composition). The area under the receiver operating characteristic curve was used as an indicator of performance. RESULTS. The mean anteroposterior-to-transverse ratio of a thyroid mass on compressed ultrasound images was significantly lower than that on noncompressed images (0.78 +/- 0.28 vs 0.92 +/- 0.30; p < 0.001). The compressibility of masses was greater for benign than for malignant lesions (0.19 +/- 0.16 vs 0.05 +/- 0.12; p < 0.001). No statistically significant association was identified between compressibility and other characteristics of a lesion. The area under the receiver operating characteristic curve for compressibility of thyroid masses was 0.78. On the basis of a cutoff value for malignancy of compressibility less than 0.10, the sensitivity, specificity, and accuracy were 72.5%, 72.9%, and 72.8%. CONCLUSION. Compressibility with an ultrasound probe is a useful criterion for differentiating benign from malignant lesions of the thyroid.