Ectopic thyroid tissue is very rare, but its prevalence increases in those with thyroid pathology. It typically occurs due to aberrant development of the thyroid gland during its migration to the pretracheal region. In this report, there are two cases of mediastinal ectopic thyroid tissue discussed, which were initially considered to be malignancies. The hospital course, diagnostic workup, including the use of computed tomography and positron emission tomography scans, and the characteristic features of the tissue are examined here. Due to the imaging characteristics, it is important to consider ectopic thyroid tissue as a differential diagnosis for mediastinal masses as encountered in these cases. Asymptomatic ectopic thyroid tissue is usually treated medically; however, patients in both of our cases opted for surgical resection of the masses even after confirmation of the origin of the tissues.
Keywords: Computed tomography; malignancy; mediastinal ectopic thyroid; positron emission tomography-computed tomography.