Ectopic Intrathyroidal Thymus Mimicking a Thyroid Nodule

Abstract

Ectopic thymus is a well-known embryological abnormality in children, despite being considered rare. To avoid unnecessary examination or biopsy, radiologists must be aware of this condition, especially in pediatric population. This report describes a pediatric patient with history of recurrent episodes of tonsillitis since 2 years of age. In the context of infectious mononucleosis, a cervical ultrasound was performed, which revealed a relatively hypoechoic lesion in the right lobe of the thyroid gland, similar to normal thymus echogenicity. Thyroid function tests were normal. After 3 years of follow-up, the intrathyroidal nodule maintained the same characteristics, having decreased in size from 12 mm to 8 mm.