A 39-yr-old man was referred for evaluation of a lump in the neck. Examination, a firm, nontender thyroid gland was felt, approximately twice normal size, with the right lobe slightly larger than the left. Serum T4 was 6.4 μg/dL (normal, 5–12), and serum TSH was 4.8 mU/L (normal, 0.4–4.6). Antithyroglobulin antibodies were positive (1:100), and antimicrosomal antibodies were not detected. A diagnosis of Hashimoto’s thyroiditis was made, and the patient was started on 0.1 mg of[ scapl-thyroxine per day. On follow-up visit, 5 months after l-thyroxine was started, the thyroid was not palpable. Serum T4 was 11.1 μg/dL, and serum TSH was 0.82 mU/L. At the 12-month follow-up visit, the thyroid was palpable, firm, but not enlarged. Serum T4 was 10.1 μg/dL, and serum TSH was 0.92 mU/L. Two years later, while the patient remained on the same dose of l-thyroxine, a firm 3.5-cm nodule was detected in the right lobe of the thyroid. His serum free T4 was 1.4 ng/dL (normal, 0.8–2.0), serum TSH was 1.82 mU/L, serum thyroglobulin was 289 ng/ml (normal, 2–60), and antimicrosomal antibodies remained undetectable. A fine needle aspiration of the nodule was performed, and it revealed a mixed population of lymphoid cells, mainly small round and small cleaved lymphocytes, with numerous plasma cells and rare clusters of atypical Hürthle cells, a pattern consistent with Hashimoto’s thyroiditis. The dose of l-thyroxine was then raised to 0.125 mg per day. Six months later, the right thyroid mass had increased to about 5 cm in diameter. There was no lymphadenopathy. In view of the rapid growth of the mass, the patient was referred for surgery, and a right hemithyroidectomy was performed. The surgical specimen contained a 5 × 4 × 3.5-cm nodule with focal areas of hemorrhage, and serial sections were taken for histologic evaluation.

These histologic features raised suspicion of low-grade MALT thyroid lymphoma, in the presence of a reactive process, probably Hashimoto’s disease.

The most striking clinical feature in this patient’s presentation was rapid, nontender enlargement of the thyroid. This is a characteristic feature of thyroid lymphomas (6). Compressive symptoms, like hoarseness, dysphagia, or dyspnea, seen in up to 30% of patients, were absent in our patient. Of note is this patient’s age and sex, because most thyroid lymphomas, including maltomas, are seen in the elderly, with a peak incidence in the seventh decade, and the female/male ratio varies from 4:1 to 8:1 (3, 6). Also, the finding of low titer of antithyroglobulin antibodies and undetectable antithyroid microsomal antibodies is unusual in patients with Hashimoto’s disease. Methods of determination of antithyroid peroxidase antibodies were not available when the patient was evaluated.serum thyroglo The presence of antithyroglobulin antibodies may have resulted in underestimation of serum thyroglobulin.In conclusion, this case illustrates that: 1) low-grade NHL of MALT-type arises in the setting of chronic autoimmune thyroiditis; 2) cytology and histology may be insufficient to diagnose MALT-lymphoma of the thyroid; 3) molecular techniques may be necessary to distinguish between MALT-lymphoma and reactive process; and 4) the nature of follow-up care and long-term results of treatment of patients with thyroid maltoma are not fully established.

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