Thyroid enlargement due to extramedullary plasmacytoma.

We report the case of a 69-year-old woman presenting with a rapidly enlarging thyroid mass as the first extramedullary symptom of plasmacytoma. Extramedullary locations are found in less than 5% of patients with multiple myeloma and can arise in any tissue. If the patient presents with extramedullary lesions and the radiologist is unaware of the underlying disease process the masses can be mistaken for disseminated metastatic carcinoma or non-Hodgkin's lymphoma.