Malignant lymphomas of the thyroid: a clinical pathologic study of 35 patients including ultrastructural observations.

The clinical and pathologic findings for 35 patients with malignant lymphoma presenting in the thyroid are reviewed. The lymphomas tended to occur in females with a median age of 65 years and clinically were manifested by a mass in the neck. The majority of patients were euthyroid and thyroid scans demonstrated cold nodules. In none of the patients was there clinical suspicion of lymphoma prior to surgery. Thirty-four of the cases were histiocytic lymphomas; the one exception; a patient with nodular poorly differentiated lymphocytic lymphoma, had histiocytic lymphoma in a subsequent biopsy of the soft tissues of the neck. Although classified as histiocytic, the lymphomas had the histologic and ultrastructural features of transformed lymphocytes or immunoblasts. Lending possible additional credence to the immunoblastic nature of these lymphomas was the histologic documentation of chronic lymphocytic thyroiditis in all 27 cases where residual thyroid parenchyma remained. This relationship suggests possible evolution of thyroid lymphomas from chronic lymphocytic thyroiditis and probably is analogous to the malignant lymphomas developing in other altered immune states, including Sjogren's syndrome. In the current study the overall 5-year survival was 54%. Patients under age 65, without local soft tissue extension or regional lymph node involvement, and with stage I disease survived the longest; a nodular histologic pattern also appeared to favorably influence the prognosis. Improved staging procedures and newer modes of therapy appear essential, particularly for those patients with clinical stage II disease and with local extension to soft tissues.