Benign Thyroidal Lesion - Intrathyroidal Ectopic Thymus

Thyroid nodules are uncommon in pediatric patients, much less prevalent than adults. Despite having a higher probability of malignancy, most thyroid nodules are benign. Intrathyroidal ectopic thymus (IET) is a rare entity due to abnormal thymic migration during embryogenesis. The diagnosis is usually incidental and patients tend to be asymptomatic. Ultrasound is the recommend diagnostic method, since IET has a typical and unique appearance on ultrasonography. It is essential to recognize and differentiate IET from malignant thyroid nodules in order to avoid unnecessary surgeries and/or invasive diagnostic procedures, such as fine needle aspiration biopsies. The risk of malignant transformation is extremely low, therefore IET can be safely managed with serial ultrasound, without any treatment.