Multiple Myeloma Presenting as Thyroid Plasmacytoma

Thyroid gland and thyroid cartilage infiltration in multiple myeloma (MM) are rare. Here, we discuss a patient who presented with hoarseness of voice and was found to have a hypodense lesion in right lobe of thyroid involving thyroid and cricoid cartilage. Fine-needle aspiration cytology with immunohistochemistry revealed extramedullary plasmacytoma of thyroid. MM was ruled out initially by serum protein electrophoresis, immunofixation, and bone marrow biopsy. Later, lytic lesions were found in multiple bones on radiation planning scan and he was finally diagnosed as case of MM with thyroid involvement. Treatment strategies of MM and thyroid plasmacytoma are also discussed briefly.