Thyroid Ultrasound > Sonographic Features > Shape and Margins

Shape and Margins

It had been previously suggested that a shape taller than wide was 92.5% specific for malignancy. This feature had fairly low (32.7%) sensitivity, however, and was not definitively confirmed later. Spherical shape was also found to be predictive of malignancy in a study. A ratio of long axis to short axis length of greater than 2.5 has been shown to demonstrate benignity, although this shape is relatively rare.

A sonolucent halo (see below image from Ultrasound Clinics Apr 2009), previously believed to be a feature of benign nodules, can be seen in 10% to 24% of papillary cancers. The finding of an irregular margin has widely varying sensitivity for malignancy (7% to 97%) and the highest interobserver variability of several sonographic features.


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