Co-Occurrence of Papillary Thyroid Carcinoma and Mucosa-Associated Lymphoid Tissue Lymphoma in a Patient with Long-Standing Hashimoto Thyroiditis
An 81-year-old female patient was admitted to a local hospital for weight loss, goiter, and hoarseness. The goiter and hoarseness had been present for about 10 years; the weight loss was 10 kg over the prior 6 months. However, there were no symptoms of fever or night sweats. She had a history of hypertension, but had no family history of cancer, and had no history of thyroid disease or radiation exposure. On physical examination, the thyroid was firm, fixed, and diffusely enlarged; however, there was no pain or tenderness. The thyroid gland measured approximately 10 cm in width and 12 cm in length. Other than the goiter, physical examination was unremarkable. Laboratory tests were as follows: white blood cell count, 6,760/µL; hemoglobin, 13.4 g/dL; platelet count, 207,000/µL; total protein, 9.5 g/dL; albumin, 3.7 g/dL; aspartate aminotransferase, 25 IU/L; alanine aminotransferase, 16 IU/L; lactate dehydrogenase, 257 IU/L (normal range, 135 to 214). Thyroid function tests: free T4, 0.79 ng/dL (normal range, 0.75 to 2.00); T3, 99.5 ng/dL (normal range, 79.8 to 200); thyroid stimulating hormone (TSH), 2.55 µU/mL (normal range, 0.3 to 5.0); and antithyroglobulin antibody level, 14.75 U/mL (normal range, 0 to 60) were within normal limits, but antithyroid peroxidase antibodies were elevated (165.22 U/mL; normal range, 1 to 60).\nInitial ultrasonography revealed diffuse enlargement of the thyroid gland, with heterogeneous background parenchyma. Transverse imaging revealed an ill-defined hypoechoic nodule measuring 3.7×3 cm in the right thyroid gland. The left thyroid gland and isthmus showed a diffuse goiter with ill-defined multiple patchy hypoechogenicities and heterogenecity (). Fine needle aspiration revealed the nodule to be suspicious for PTC. Thereafter, the patient was admitted to our hospital for surgery. Preoperative computed tomography (CT) of the neck revealed a diffusely enlarged thyroid gland with nodules in both lobes ().\nA total thyroidectomy and right and left central neck node dissection was performed. Gross and microscopic examination disclosed a 3.7×3.0 cm papillary carcinoma in the right thyroid gland (). There was minimal extrathyroidal extension, all surgical resection margins were negative and no metastatic lymph nodes were found (pathologic TNM staging, T3N0Mx, stage III). Background thyroid tissue showed diffuse lymphocyte infiltration, the presence of Hürthle cells, small follicles with scanty colloid, and germinal center formation, which are all characteristics of HT. The left thyroid gland weighed 116 g and was measured 9.6×6.9×2.9 cm; microscopic histopathology revealed a nodular proliferation of small B cells, with a lymphoepithelial lesion suggestive of MALT lymphoma in the left thyroid gland. Much of the normal thyroid architecture was replaced by dense, diffuse infiltrates of atypical small B lymphocytes, showing strong CD20- and lambda light chain-immunopositivity, and an absence of κ light chain (). IgH gene rearrangement assay confirmed the diagnosis of MALT lymphoma.\nBone marrow examination is necessary in order to set the stage of lymphoma. However, the patient refused invasive evaluation due to her age. Postoperative neck CT and 18F-fluorodeoxyglucose positron emission tomography of the neck performed within 1 month of surgery demonstrated no persistence or recurrence of either neoplasm. There was no evidence of lymph node enlargement in the neck, mediastinum, or abdomen. Although a bone marrow biopsy was not performed, MALT lymphoma was considered to be confined to the thyroid gland, corresponding to stage IE according to Ann Arbor classification.\nThe patient is currently taking levothyroxine as a sole postsurgical therapy. Based on age and health status, radioiodine treatment was not administered. Symptoms of hoarseness and weight loss improved after surgery. One year after surgery, a thyroid function test was performed and antithyroglobulin antibody levels and thyroglobulin levels were measured (free T4, 1.61 ng/dL; T3, 122.1 ng/dL; TSH, 0.00 µU/mL; antithyroglobulin antibody, 11.02 U/mL; thyroiglobulin, 0.227 ng/mL). Neither tumor has recurred during the 1-year follow-up period.