Incidental thyroid abnormalities identified on neck US for non-thyroid disorders

Incidental thyroid abnormalities detected on US examinations in children have not been well documented.

To determine prevalence of incidental thyroid abnormalities depicted by US in children and to describe the spectrum of appearances.

Retrospective analysis of clinical and US findings in children who had neck US from January 2006 to December 2007.

Of 1,228 neck US exams, thyroid was depicted in 287 children (mean age = 6.2 years). Incidental thyroid abnormalities were detected in 52 (18%) (mean age = 8.1 years). In 35 there were small (<4 mm), well-defined cysts, some with a hyperechoic punctate focus. In nine there were hypoechoic, solid nodules with smooth, straighter margins with echogenicity similar to thymus, suggesting intrathyroid ectopic thymus (mean age = 2.5 years). In three others there were tiny hyperechoic foci without nodules. Other abnormalities included hypoechoic target-like lesions (n = 2), isoechoic nodule (n = 1), multiple hypoechoic foci (n = 1) and non-visualized thyroid lobe resulting from adjacent abscess (n = 1). None of the children developed thyroid dysfunction or malignancy.

There is a spectrum of incidental thyroid abnormalities in children. These US findings should be interpreted cautiously, avoiding unnecessary referrals and investigations. Intrathyroid ectopic thymus is more common than previously thought, occurs much more frequently in younger boys and should be considered if the lesion has US characteristics of thymus.