Conditions: Substernal Goiter

What is a substernal goiter?

A substernal goiter is a goiter that extends into the chest cavity behind the sternum (breastbone). Because a large thyroid gland tucked away/ buried behind bone may not be noticeable visually or by feeling the neck, the component of the thyroid behind the sternum may grow to be very large before causing symptoms, such as shortness of breath due to compression of the trachea (windpipe).

Example of a large substernal goiter displacing the trachea

Example of normal thyroid

A normal sized thyroid does not extend below the collarbones and sternum into the chest cavity, nor does it narrow or displace the trachea (windpipe) or esophagus. An adult thyroid gland typically weighs about 25 grams, and each lobe measures about 5 cm long (top to bottom), 3 cm wide (left to right), and about 2 cm thick (front to back), though these values vary between individuals.

How is a substernal goiter evaluated?

While ultrasound is usually the best imaging choice for thyroid glands, the sternum and ribs prevent sound waves from adequately assessing any portion of the thyroid that has passed into the chest. For this reason, CT imaging is typically undertaken to evaluate the size and any anatomic distortion caused by the substernal goiter.

When a goiter does have some tissue in the neck that is accessible to ultrasound, undertaking ultrasonography and proceeding with a fine needle aspiration biopsy, if indicated is useful to gauge the risk for thyroid cancer before treatment, which is usually surgical. The surgical planning and approach may differ when thyroid cancer is suspected.