Thyroidal prelymphoma.

We treated a 32-year-old man with "thyroidal prelymphoma", morphologically resembling Hashimoto's thyroiditis and associated with monoclonal gammopathy (IgG, lambda). Immunohistochemistry revealed intracytoplasmatic monoclonal immunoglobulin (IgG, lambda) containing lymphoid cells in the interstitium of the thyroid tissue. After total thyroidectomy had been performed, the monoclonal immunoglobulin disappeared. Three years have passed since the surgery and this writing, there has been no recurrence. The existence of thyroidal prelymphoma suggests that chronic antigenic stimulation might produce lymphocytes which are more susceptible to neoplastic change (Hashimoto's thyroiditis----thyroidal prelymphoma----malignant lymphoma of the thyroid).