Ectopic Thyroid Gland (ETG)
- ETG is a developmental malformation of the thyroid gland in which the thyroid gland lies completely outside its normal location in the pretracheal lower neck. Instead, the ectopic thyroid tissue can be found anywhere along its embryonic course (ie, from the foramen cecum to its normal location in the lower neck).
- Most patients with ETG are asymptomatic. However, ETG patients with normal thyroid function can become hypothyroid during puberty, menstruation, pregnancy, infections, trauma, and surgery. Hypothyroidism may trigger enlargement of an ETG, which can cause symptoms such as dysphagia and dyspnea. Hyperthyroidism is very unusual.
- Key Diagnostic Features: The thyroid gland is not seen in its normal location. Instead, a well defined, hyperdense, enhancing, midline mass is seen anywhere along the embryonic course of the thyroid gland, as mentioned above. Intratracheal, intraesophageal, mediastinal and cardiac locations are rare. Nuclear medicine evaluation can be helpful. An ETG can undergo malignant transformation.
- DDx: Lymph node; thryoglossal duct cyst
- Rx: Observation, thyroxin therapy, and surgical resection