Thyroid Tissue at the Wrong Site (Ectopic)
Ectopic tissue is normal tissue that is found in a part of the body where it is not usually meant to be. During normal development, the thyroid forms at the base of the tongue, and later drops down into the neck. A remnant is left behind which usually involutes (goes away). If the thyroid does not descend normally, it may remain at the base of the tongue (called a lingual thyroid) or within the muscles of the neck. In 60% of patients, this is the only thyroid tissue they have. This thyroid tissue is often abnormal and functionally insufficient. In other children, the thyroid may extend into the chest (mediastinum) or develop close to the heart. These patients often have normal thyroid tissue in the neck. If a mass is identified in these locations, a thyroid scan (technetium-99m or iodine-123) is used to identify the ectopic thyroid gland. If surgery is considered, these scans will help determine if the ectopic thyroid is the only thyroid tissue. If symptoms of compression are the reason for the evaluation, medicines that cause thyroid suppression may cause the ectopic tissue to shrink and relieve the symptoms. Surgery is indicated for diagnosis or persistent symptoms despite medical therapy.
Article and graphics adapted from O'Neill: Principles of Pediatric Surgery. © 2003, Elsevier.