Key Points

• Substernal goiters account for less than 10% of all goiters.
• Most substernal goiters are pathologically benign.
• Most substernal goiters arise from orthotopic cervical thyroid and are supplied by the inferior thyroid artery.
• Most substernal goiter patients are symptomatic due to mass effects on trachea or esophagus.
• Most substernal goiter patients are euthyroid.
• Most substernal goiters are adequately diagnosed and evaluated by CT.
• The diagnosis of substernal goiter is an indication for surgery.
• Most substernal goiters can be removed transcervically.
• Most substernal goiters are anterior or lateral to the trachea, as opposed to posterior.
• Most substernal goiter patients experience an improvement in symptoms after surgery and can be treated without complications.

The definition of goiter has been debated, and classifications have been proposed based on clinically estimated size or volume, imaging-based estimates of size or volume, and definitive measurements of pathology specimens. Despite this, any thyroid tissue extending significantly behind the sternum or in some cases below the clavicles, or any thyroid tissue found within the confines of the thoracic cavity, can be considered abnormal tissue extension. These situations are classified as substernal goiter. Other similar terms include retrosternal, subclavicular, infraclavicular, intrathoracic, and mediastinal..