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 aerodigestive axis or vascular structures are not technically possible in the absence of IV contrast administration. For these reasons, 18FDG-PET/CT utilizing contrast administration should be considered for most patients with extensive disease. Metastasis to the thyroid is rare and represents 5.5 % of biopsied thyroid malignancies. It is commonly found with cancers originating from the breast, renal cell, lung, melanoma, and colon. Direct invasion from adjacent structures such as the pharynx, larynx, trachea, or oesophagus has been reported (Fig. 10). Metastatic disease has a non-specific appearance. Presence of ITNs in patients with another known malignancy is a common clinical problem