Ectopic colloid goiter in mediastinum with normal thyroid gland.

Ectopic thyroid tissue is a rare developmental abnormality involving aberrant embryogenesis of the thyroid gland during passage from the primitive foregut to the pretracheal position. The most frequent position is the base of the tongue (lingual thyroid); however, it has been described in other sites, such as the submandibular region, trachea, mediastinum, and subdiaphragmatic regions.Here, we report a case of an adenomatous goiter that developed in mediastinal thyroid tissue without any connection to the pretracheal thyroid gland.