The thyroid gland with low uptake lesions: evaluation by ultrasound.

An ultrasound examination was performed in 401 patients who had isotopically cold, solitary lesions of the thyroid gland. Of the parameters studied, the level of echoes was the most useful in making the sonographic diagnosis: the rate of malignancy was extremely low both in hyperechoic and echo-free lesions. The presence of a peripheral, complete "halo" appeared to be helpful in differentiating benign lesions from malignant lesions. Approximately 20-25% of the lesions thought to be solitary on the radionuclide study were found to be multinodular on US. When fine-needle aspiration biopsy was used with US the need for surgical exploration of the thyroid gland was obviated in selected cases.