[A pathological study of primary malignant lymphomas of the thyroid]

Thirty cases of a primary malignant lymphoma (ML) have been studied clinicopathologically and immunohistochemically. The average age of the patients was 59.1 years, and the ratio of males to females was 1:1.7. According to the Kiel classification of MLs, 53.3% had a low grade malignancy and 46.7% were a high grade malignancy. Therefore, the number with a low or a high grade malignancy was almost equal. Most of the low grade malignancies were ML, centroblastic centrocytic, and most of the high grade malignancies were ML, lymphoblastic. From histopathological and immunohistochemical studies, most cases were considered to be of B-cell origin and two thirds of the cases were regarded as being of a follicular center cell origin. Prognosis was better than that of other MLs. Finally, MLs of the thyroid were found combined more frequently with chronic thyroiditis of the Hashimoto type than malignant epithelial neoplasms.