Out of 78 cases of non-Hodgkin's lymphoma (11.5%) and 263 cases of thyroid cancer (3.4%), 9 cases of primary malignant lymphoma of the thyroid were treated at our hospital from 1986 to 1996. These patients comprised 5 males and 4 females ranging in age from 44 to 84 years (median, 68 years). Histopathologically, 5 cases were diffuse mixed type, 3 cases were diffuse large type, and only one case was small lymphocytic type according to the Working Formulation classification. The clinical stage was classified as stage I in 2 cases, stage II in 5 cases and stage III in 2 cases.
In 7 cases rapid enlargement of tumor within 3 months was observed and in 4 cases Hashimoto's thyroiditis was performed.
We performed fine needle aspiration biopsy (FNA) in 8 patients, but only 2 cases were diagnosed accurately, and ultrasonography was used in 5 patients, but only 2 cases were diagnosed accurately; thus, FNA and ultrasonography were not useful to detect and diagnose thyroid malignant lymphoma. Patients with Hashimoto's thyroiditis and rapid enlargement of the tumor should be considered to have malignant lymphoma and immediate open biopsy should be performed.
Of our 9 patients, 4 patients were treated with combined chemotherapy and radiation, 2 with surgery, chemotherapy and radiation, 2 with radiation only, and one with chemotherapy only, and two patients in stage III died soon after treatment. Thyroid malignant lymphoma does not always show a good prognosis, and it is important to diagnose in the early stage and to start radiotherapy combined with chemotherapy immediately.
