Malignant lymphoma of the thyroid. A 30-year clinicopathologic experience and an evaluation of the presence of Epstein-Barr virus.

Lymphoma of thyroid is uncommon, and Epstein-Barr virus (EBV) is found in many lymphomas. We studied the clinicopathologic characteristics in Hong Kong Chinese and analyzed the presence of EBV in thyroid lymphomas by reviewing data collected during 3 decades. We studied EBV gene expression by in situ hybridization and immunohistochemistry. Primary thyroid lymphomas were found in 23 patients (diffuse large B-cell lymphoma, 18; marginal zone B-cell lymphoma, 4; plasmacytoma, 1), and secondary lymphomas were found in 9 patients (diffuse large B-cell lymphoma, 3; Burkitt lymphomas, 2; Burkitt-like lymphoma, 1; hairy cell leukemia, 1; nasal T-cell and natural killer cell lymphoma, 1; and intestinal T-cell lymphoma, 1). Primary thyroid lymphomas were large (mean, 7 cm), found commonly in older women, and often misdiagnosed as undifferentiated carcinomas. Fine-needle aspiration was not helpful for diagnosis. Fifteen patients had Hashimoto thyroiditis. A history of thyrotoxicosis was found in 3 patients, and coexistence of 3 diseases (papillary microcarcinomas, primary thyroid lymphoma, and Hashimoto thyroiditis) was found 4 patients. The 5-year survival rate for primary thyroid lymphoma was 53%. Combined surgery and radiotherapy seemed to be the best treatment. Secondary thyroid lymphomas often were asymptomatic. EBV messenger RNAs were detected in 1 primary and 1 secondary thyroid lymphoma. The EBV gene expression in primary thyroid lymphoma showed a type II latency pattern. Thyroid lymphomas in Chinese had important clinicopathologic features. EBV may have a role in a subset of cases.