Primary plasmacytoma of the thyroid: a case report and comparative literature study between Western nations and Japan.

A 52 year old man presented with primary thyroid plasmacytoma. The patient was initially followed up for thyroid dysfunction. The histological examination of the removed thyroid revealed a proliferation of mature and immature plasma cells indicative of plasmacytoma with Hashimoto's disease. After radiotherapy (40 Gy) to the neck following right hemi-thyroidectomy, the patient is currently alive and well 3 years after diagnosis without any evidence of tumor. The immunohistological examination of the removed thyroid showed monoclonality for immunoglobulin G-Kappa light chains. Sixty-six literature cases of primary thyroid plasmacytoma were reviewed and comparison of the clinical and histological characteristics between Japanese and Western cases noted. The incidence of the patients with antithyroid antibody was significantly lower (P < 0.01) in Western patients (42.9%) than in Japanese patients (87.5%). The higher incidence of thyroid dysfunction and Hashimoto's disease in Japan in comparison with Western nations was well reflected in the incidence of antithyroid antibody.