CT diagnosis of mediastinal thyroid.

Computed tomography (CT) is capable of specifically diagnosing mediastinal thyroid as the cause of a mediastinal mass. Five representative cases illustrate characteristic features of substernal thyroid. These include: (1) anatomic continuity with the cervical thyroid; (2) focal calcifications; (3) relatively high CT number; (4) rise in CT number after bolus administration of iodinated urographic contrast material; and (5) prolonged enhancement after contrast administration. While not all of these features are present in each case, a combination of these should permit accurate diagnosis in most cases.