ESPE Abstracts

Background: Intrathyroidal ectopic thymic tissue is one of the rarest congenital abnormalities. Ectopic thymus tissue can be detected in various locations from the mouth or the base of the skull to the superior mediasteneum. We report here three cases of intrathyroidal ectopic thymus tissue who presented as thyroid nodules in different ages.

Cases: Case 1: a 10-year-old girl had a guatr and her thyroid function tests were normal. Thyroid US showed a hypoechoic calcified nodule (10×4 mm) in the right lobe. There was no regional lymphadenopaty. Fine-needle aspiration biopsy was recommended (FNAB), but the parents preferred to excision of the nodule. Right lobectomy was performed and pathologycal examination showed an ectopic intrathyroidal thymus tissue. Case 2: a 7-month-old baby was referred to our clinic because of thyroid nodules which were detected incidentally. She was euthyroid. Thyroid US was repeated and showed a hypoechoic nodule (7×5×9 mm) with multiple hyperechoic areas in the left lobe and a similar hypoechoic nodule in the right lobe which were reported as ectopic thymic tissues. FNAB was not done because it was an invasive diagnostic procedure. During 1 year follow-up, nodular enlargement was not seen. Case 3: a 4-month-old baby was referred to our clinic because of suspected thyroid nodule which was detected during neck US for torticollis. His thyroid function tests was normal and repeated thyroid US showed an intrathyroidal ectopic thymic tissue. There was no nodular enlargement during 18-month follow-up.

Conclusions: Ultrasonographic findings are tipic for thymic tissue. The increasing use of thyroid US may result in an increased detection of intrathyroidal thymic inclusions that should be considered in the differential diagnosis of thyroid nodules in children and adolescents. If US results are inconclusive and further evaluation is needed, a biopsy may be useful for confirmative diagnosis.