Intrathyroidal ectopic thymus in children: a sonographic survey.

Abstract

Intrathyroidal ectopic thymus (IET) is being increasingly reported in the radiology literature. Most of the reportsare of individual cases or small series and prevalence and natural course of the pathology is not well known. The purpose ofthis study is to establish the prevalence of IET in children and report long term follow-up results. In180 children who were examined by ultrasound (US) for other reasons, 7 patients were indentified with IET. Together with theother seven children who were already under follow-up for IET (diagnosed using US criteria), these 14 patients were followedup with US for 30 months. Size, shape, location, echotexture and internal echoes of the lesions were evaluated. Therewere 16 lesions in 14 children. The most common appearance was a fusiform hypoechoic lesion, with punctate and linear internalechoes and well-defined but slightly irregular borders located posteriorly in the lower thirds of the thyroid. In follow-up,there were no changes in echotexture, shape or border. In 3 patients, the lesion became slightly smaller, in a 10-year-old boyslightly larger, and in an 11-year old boy the lesion disappeared. In a patient with bilateral lesions, one lesion slightly decreasedin size. IET in children may be more common than thought. Its growth reflects that of a normal thymus. Awarenessof this entity is important in order not to misdiagnose them, especially as papillary cancer, and to prevent unnecessaryinterventions.