Substernal Goiter

Excerpt

An enlarged thyroid gland is termed a goiter. The thyroid usually grows anteriorly and/or laterally. The thyroid gland is covered by thin muscles, subcutaneous fat tissue, and skin and does not meet significant resistance while growing. When enlarged, it is typically visible and easily palpable, but may be complicated by body habitus. If the thyroid gland grows inferiorly and passes through the thoracic inlet into the thoracic cavity, it is termed a "substernal goiter." An alternative term is "retrosternal goiter". Substernal goiter may involve one or both the lobes of the thyroid gland and may cause deviation and/or compression of the trachea, and less commonly esophagus or venous structures. Tracheal compression has been reported in 35% to 73% of substernal goiters. Up to 10% of substernal goiters are located in the posterior mediastinum, and 90% of that 10% posterior mediastinal goiters are right-sided, as left-sided subclavian arteries and the aortic arch do not allow for left-sided expansion. Some studies define substernal goiter, if any portion of the thyroid gland goes down through the thoracic inlet, whereas others define if 50% or more of the thyroid is below the thoracic inlet. The difference in the definition explains, in part, the variability of results among studies. If the lower tip of the thyroid goes back above the thoracic inlet when the patient extends his/her neck, the abnormality is positional and does not count as a substernal goiter.