Substernal goiter is a condition that is readily overlooked and often not recognized until a distinctly serious situation has arisen. It is not discussed extensively in the literature, and except in clinics where thyroids are dealt with in numbers it is often not looked for except when producing unmistakable pressure symptoms.
From our experience with this condition, it is one that readily lends itself to prevention, by occasional examinations to determine the progressive descent of a goiter and by early removal of those goiters tending to descend into the thorax. I have repeatedly stated and written and I urge again that progressive descent of a goiter or the location of adenomas or cysts of the thyroid where they may, or tend to, enter the mediastinum should be an outstanding indication for their surgical removal.
Goiters that have entered the mediastinum and have deviated and flattened the trachea have done so,
LAHEY FH. SUBSTERNAL GOITER. JAMA. 1926;87(16):1282–1287. doi:10.1001/jama.1926.02680160030010