Case 96-3
History/Physical Findings:A 62-year-old white woman presented with stridor due to a neck mass which was clinically suspicious for multinodular goiter. The patient was placed on Synthroid, however, the gland continued to enlarge over the course of three weeks as evidenced by increased stridor and dysphagia. She reported a 40 pound weight loss over the previous six months. Additional symptoms included chronic fatigue and occasional chills. She reported a 36 pack year history of tobacco use. Thyroid studies performed at the initial consultation included: total thyroxine 19.0 ug/dL (normal range=4.5-10.9 ug/dL), TSH 0.04 uIU/mL (normal range = 0.4-6.0 uIU/mL) and thyroid hormone uptake 27% (normal range = 25-35%). Due to the compression of the trachea a total thyroidectomy was performed. The gland measured 14 x 12 x 7 cm and weighed 460 grams.
  
 
Discussion:H&E stained sections are shown identifying a diffuse large lymphocytic infiltrate with rare residual thyroid follicles identified. A B cell marker, CD 20 (L26), marked the lymphocytes. The T cell markers, CD 3 and CD 45RO, were negative. Kappa and lambda were non-contributory. A cytokeratin cocktail highlighted the residual thyroid follicles but the lymphocytes were negative.
Primary lymphoma of the thyroid consists of approximately 8 percent of all thyroid malignancies whereas involvement of the thyroid by systemic lymphoma or leukemia can be found in approximately 10 % of cases.
Primary thyroid lymphoma is usually seen in patients in their sixties with a female to male ratio varying from 2:1 to 8:1. The duration of symptoms is usually short and include hoarseness, dysphagia and or dyspnea. These symptoms are usually due to extra-thyroid extension. Most patients are euthyroid.
Upon gross examination, the tumor presents as a solid mass with a homogenous bulging surface exhibiting the characteristic fish-flesh appearance. The interface between normal gland and tumor is usually ill-defined. Necrosis and hemorrhage are unusual findings in lymphomas of the thyroid.
The majority of primary thyroid lymphomas are non-Hodgkins lymphomas and are usually large cell lymphomas with a B cell phenotype. The second most common lymphoma is the immunoblastic type although poorly differentiated and intermediate types have also been reported.
In approximately 80% of the cases of thyroid lymphoma the residual uninvolved gland exhibits features of autoimmune thyroiditis (Hashimotos's or lymphocytic type). It is speculated that the presence of thyroiditis predisposes the patient to lymphoma as opposed to the thyroiditis occurring after the lymphoma. However, the percentage of patients with thyroiditis who develop lymphoma is low.
Diagnosis:Primary malignant lymphoma of the thyroid References:
Contributors:David C. Winston, M.D., PhD Donald J. Innes, Jr., M.D.
Questions should be addressed to dji@virginia.edu
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