Primary thyroid lymphoma: comparison of CT and US assessment.

Sixteen patients with primary thyroid lymphoma were studied with computed tomography (CT) and ultrasonography (US), and findings were compared. In 13 of 16 patients, detection of the primary tumor with US and CT were comparable. US was superior in one case, and CT in another. One tumor was not detected with either technique. Thyroid lymphomas appeared as extremely hypoechoic masses intermingled with echogenic structures. Although echogenicity of unaffected thyroid tissue was also low because of coexisting Hashimoto thyroiditis, thyroid lymphomas were relatively well differentiated as markedly hypoechoic areas. Five tumors showed contiguous spread into both thyroid lobes. US and CT were equally sensitive in detection of superficial lymphomatous nodes (seven of 16 cases). CT was superior to US in the definition of tumor extent in two patients with intrathoracic tumor extension and in one with laryngeal invasion. In patients with suspected thyroid lymphoma, CT should be the primary radiologic technique used for diagnosis and staging; US will be useful in local follow-up.