[Primary plasmacytoma of the thyroid--report of an autopsy case and review of the literature in Japan].

Primary extramedullary plasmacytoma (PEMP) of the thyroid is rare. Only nine patients with PEMP of the thyroid have been reported in Japan to date. We describe an additional autopsy case with PEMP of the thyroid and review of the literature in Japan. A 67-year-old women complaining of swelling of the anterior neck exhibited thin scalp hair, edematous face and a giant, hard, nodular goiter. Laboratory examination showed elevated levels of ESR, collagenous reaction, gammaglobulin, and a M-bow of the IgG-k type in immunoelectrophoresis. No Bence-Jones protein was found in the urine. Thyroid function test revealed a subclinically hypothyroid state, showing a T3 of 1.32 ng/ml, a T4 of 10.0 micrograms/dl, a TSH of 23.4 microU/ml and positive thyroid antibodies. The scintigram and the CT scan of the thyroid showed deviation of the trachea by the thyroid tumor and calcification within homogeneous thyroid gland. She underwent total thyroidectomy because of suspected malignancy. The histological examination of the removed thyroid weighing 117gr revealed a proliferation of plasma cells and lymphocytes and small amounts of atrophied thyroid follicles. The immunohistological examination of the removed thyroid showed the monoclonality to IgG-k chain. Plasma cells were stainable with methylgreenpyronine. Twenty-six months after thyroidectomy, she died due to progressive emaciation, anemia, hypoalbuminemia and ascites. Postmortem examination revealed widespread metastasized plasma cell tumors in the liver, intestine, spleen and mesentery with ischemic changes in heart and kidney. Based on our autopsy case and the nine cases reported in Japan, clinical and histological characteristics of PEMP of the thyroid were discussed.