Thyroid dysgenesis thyroid gland may be located anywhere along the path of the descent of the thyroid during its embryological development, although it is most commonly located at the base of the tongue, just posterior to the foramen cecum of the tongue. In this location, an aberrant or ectopic thyroid gland is known as a "lingual thyroid". If the thyroid fails to descend to even higher degree, then the resulting final resting point of the thyroid gland may be high in the neck, such as just below the hyoid bone. Parts of ectopic thyroid tissue ("accessory thyroid tissue") can also occur, and
Computed tomography of the thyroid iodine (RAI) ablation is an option, especially in patients with distant metastasis, tumours larger than 4 cm, or extra-thyroidal disease extension. Ultrasound examination is usually adequate in evaluating primary tumours and cervical lymph nodes. Preoperative cross-sectional imaging with CT or MRI is indicated if there is a concern for local invasion that may alter the patient’s staging as well as surgical approach (Figs. 4, ,55 and 6)6) . Some thyroid primaries may be small, diffuse, or multifocal and therefore may be occult on imaging (Fig. 4) . In patients with known thyroid malignancies, a non-enhanced exam is preferred due to