Thyroid Ultrasound > Top 10 Pathology > 7. Metastasis/Lymphoma

Lymphoma and Metastatic Disease

Lymphoma: Primary lymphoma of the thyroid is uncommon, accounting for 2% of extranodal lymphomas and less than 5% of all malignant thyroid tumors. Most thyroid lymphomas are non-Hodgkin lymphomas. Patients present with a rapidly enlarging painless neck mass. Lymphomas may occur in the setting of Hashimoto thyroiditis. Mostly occurs in 7th decade of life, with a female to male ratio of six to one.

On ultrasound, thyroid lymphoma is characteristically very hypoechoic (see below image from Ultrasound Clinics Apr 2009) with a pseudocystic pattern (increased through transmission) similar to lymphoma seen in other organs, such as the liver or lymph nodes. 

Metastasis: Metastatic disease to the thyroid is extremely rare, with primaries from kidney, colon, breast, lung and melanoma. The rate of malignancy in FDG metabolically active thyroid ‘‘incidentalomas’’ ranges from 26.7% to 80%, with the vast majority of malignancies representing primary thyroid carcinomas, not metastatic disease. Although the standardized uptake values were higher in malignant nodules than benign nodules in most studies, FNA is usually indicated for definitive assessment.

On sonography, metastases to the thyroid have a nonspecific appearance and are usually solid, noncalcified, hypoechoic nodules and can be hypervascular.

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