From the Guidelines
Ectopic thyroid is a rare developmental abnormality where thyroid tissue is located outside its normal position in the neck, and it can be diagnosed using Tc-99m pertechnetate or I-123 scintigraphy if it is a diagnostic consideration for an indeterminate prevascular or visceral mediastinal mass. Ectopic thyroid tissue can be found in various locations, including the base of the tongue, neck, chest, or abdomen, and its presence can be confirmed using imaging studies such as Tc-99m pertechnetate or I-123 scintigraphy, with I-123 scintigraphy being preferable due to its higher uptake in thyroid tissue and less background activity 1. Some key points to consider about ectopic thyroid include:
- It is a rare developmental abnormality
- It can be located in various areas outside the normal position in the neck
- Diagnosis can be made using Tc-99m pertechnetate or I-123 scintigraphy
- Treatment depends on symptoms and may include thyroid hormone replacement therapy or surgical removal
- Regular monitoring with thyroid function tests is important to ensure proper hormone levels are maintained. In terms of diagnosis, I-123 scintigraphy may be preferable over Tc-99m pertechnetate due to its higher uptake in thyroid tissue and less background activity 1. It is also important to note that ectopic thyroid tissue can produce adequate thyroid hormone, but some patients may experience symptoms of hypothyroidism if the tissue cannot produce sufficient hormones. Overall, ectopic thyroid is a rare condition that requires proper diagnosis and treatment to manage symptoms and maintain proper hormone levels.
From the Research
Definition and Prevalence of Ectopic Thyroid
- Ectopic thyroid tissue is a rare entity resulting from developmental defects at early stages of thyroid gland embryogenesis, during its passage from the floor of the primitive foregut to its final pre-tracheal position 2.
- The specific prevalence of ectopic thyroid tissue accounts for about 1 case per 100,000-300,000 persons, and one in 4,000-8,000 patients with thyroid disease show this condition 3.
- Ectopic thyroid tissue can be found along the path of descent of the developing thyroid primordium from the foramen caecum to the isthmus of the thyroid and up to the base of the diaphragm 4.
Clinical Presentation and Diagnosis
- Patients with ectopic thyroid tissue may remain asymptomatic or present with swelling in the neck, symptoms such as dysphagia, dysphonia, dyspnea, and features of hypothyroidism 4.
- The diagnosis is usually made on clinical examination, laboratory tests, imaging studies, and cytology, with thyroid scintigraphy being an important imaging tool and the gold standard for the diagnosis of ectopic thyroid tissue 4.
- Ultrasonography, CT scan, MRI, biopsy, and thyroid function tests are also used in the diagnostic management of thyroid ectopy 3.
Treatment and Management
- Asymptomatic euthyroid patients with ectopic thyroid do not usually require therapy but are kept under observation 3.
- For those with symptoms, treatment depends on the size of the gland, nature of symptoms, thyroid function status, and histological findings, with surgical excision often required as treatment for this condition 3.
- Radioiodine ablation is reserved for recurrent disease, and levothyroxine suppression therapy may be used in more refractory cases 2.
Rare Cases and Theories
- Dual thyroid ectopia, where ectopic thyroid tissue is simultaneously present at two different abnormal locations, is a very rare developmental defect 4.
- A "entoderm migration" theory has been proposed to explain distant ectopic thyroid tissues based on embryonic development perspective, particularly for cases where ectopic thyroid tissue is found in organs or tissues far from the thyroid gland 5.