Mediastinal ectopic thyroid mass with normal thyroid function and location: Case report.

INTRODUCTION: Mediastinal Ectopic Thyroid Gland is a rare entity, accounting for 1% of all mediastinal tumours. Here, we present a rare case of mediastinal mass that was proved to be an ectopic thyroid with normal thyroid function tests and normal thyroid gland in the cervical location.

CASE PRESENTATION: A 32-year-old lady had a road traffic accident, with the incidental discovery of a mediastinal mass on chest radiography. Thyroid function tests were normal. CT scans of the neck and chest revealed a large mediastinal mass compressing the trachea from the left side and extending to the superior part of the anterior mediastinum with normal thyroid gland in the cervical position. Midline Partial Sternotomy was done with complete surgical excision of the mass. It was well circumscribed, multinodular, had firm inconsistency, and grossly looked like a thyroid tissue. Histopathology revealed ectopic thyroid tissue negative for malignancy. Postoperative thyroid ultrasound showed normal thyroid lobes in the neck.

DISCUSSION: Ectopic thyroid tissue (ETT) occurs due to failure of the thyroid gland to migrate from foramen ceacum to its normal position in the cervical region in front of the trachea. The most common site of ETT is lingual thyroid and accounts for about 90% of all cases reported in the literature. ETT in the mediastinum is very rare, with only a few cases reported in the literature.

CONCLUSION: ETT in the mediastinum is very rare and can be associated with normal thyroid function and normal thyroid anatomical location. It should be differentiated from substernal goiter.