Plasmacytoma of the thyroid: a case report, a study with use of the immunoperoxidase technique, and a review of the literature.

A case of solitary plasmacytoma of the thyroid is reported. A monoclonal component (IgG lambda) was identified in the serum of the patient and disappeared after total thyroidectomy and radiotherapy. The use of the immunoperoxidase technique on thyroid, bone marrow, and lymph node specimens allowed us to demonstrate the production of IgG lambda by the tumor, and to rule out the possibility of multiple myeloma. Previously reported cases are reviewed (15 cases). The diagnostic criteria, the association with thyroiditis, and the treatment of this rare disorder are discussed.