LearningRadiology - Substernal Thyroid Mass

Thyroid Masses

• Extension of a thyroid goiter arising in the neck down into the thorax is rare

• Most (75-80%) arise from lower pole or isthmus of the thyroid and extend into anterior mediastinum

• Some arise from posterior aspect of the thyroid and extend into posterior mediastinum, almost always on the right

• Usually nodular, colloid goiters

•Thyrotoxicosis and carcinoma are rare

• Thyroid mass is typically well-encapsulated and may show degeneration (calcification)

• On CT, they usually contrast enhance and many times are found to contain calcification. The contrast enhancement is prolonged.

• Most patients are asymptomatic

X-ray

• Sharply defined, smooth or lobulated soft tissue mass which characteristically displaces the trachea

• They do not usually project below the arch of the aorta differentiating them from thymomas and teratomas

• Those in the posterior mediastinum characteristically interpose between the trachea in front and the esophagus in back

• Curvilinear calcifications are highly suggestive of a degenerated thyroid adenoma

• Radioisotope scan is diagnostic