Primary thyroid lymphoma associated with Graves' disease

We report herein a case of thyroid mucosa-associated lymphoid tissue (MALT) lymphoma in a patient receiving antithyroid drug therapy for Graves' disease. A 75-year-old woman first presented with finger tremor and was diagnosed with Graves' disease on the basis of clinical and laboratory findings. Three years later, she presented with rapid and painless enlargement of the thyroid. Ultrasonography revealed a circumscribed hypoechoic area bilaterally in each lobe of the thyroid, and fine-needle aspiration biopsy showed diffuse monotonous infiltration of small- to medium-sized atypical lymphoid cells. Ga-67 scintigraphy was positive exclusively in the thyroid. After total thyroidectomy, the patient received radiation therapy for treatment of stage IE primary thyroid lymphoma. Results of histological examination, immunohistochemical analysis, and flow cytometric analysis confirmed MALT lymphoma. To our knowledge, there have been few published reports of primary thyroid lymphoma associated with Graves' disease. Our experience with this case, though rare, indicates that an enlarged thyroid in cases of Graves' disease should be examined carefully for primary thyroid lymphoma.