The nonspecificity of the thyroid halo sign.

In a series of 28 patients with solitary solid thyroid masses, 10 of the patients had a mass surrounded by a rim of decreased echoes or by an echo-free rim, previously termed the halo sign. Eight of these lesions were benign, being either adenomas or benign nodules; however, two halos were also demonstrated surrounding proven carcinomas. The presence of the halo in both benign and malignant disease is illustrated, and the possibility of pericapsular inflammatory infiltrate as its underlying anatomic correlate is suggested.