Computed tomography of the thyroid bone, before it loops posteriorly and inferiorly to the hyoid bone. Then it continues its descent into the infra-hyoid portion of the neck, anterior to the trachea, thyroid cartilage, and thyroid membrane. Any thyroid residual along the descent course may lead to the development of ectopic thyroid glands. Thyroid carcinomas, thyroiditis, and goiter may develop within any ectopic thyroid tissue. Thyroid scanning with technetium-99 m (Tc99m) plays an important role in detecting orthotopic and ectopic thyroid tissue. Both CT scans and US can help detect ectopic tissue when a lesion demonstrates imaging and enhancement characteristics of thyroid tissue. The absence
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