Primary Plasmacytoma of Thyroid Gland—an Interesting Case Diagnosed By FNAC

Introduction: Primary plasmacytoma of the thyroid gland is a rare disease. Extramedullary plasmacytoma (EMP) comprises 3-5% of all plasma cell neoplasm. Case report: A 57-yearsold female presented with a large thyroid swelling involving the left lobe and isthmus, firm in consistency and moved a little with deglutition. CT scan revealed a large solid tumor (9.5 cm in greatest dimension) affecting thyroid gland. CT scan report gave differential diagnoses of plasmacytoma and metastatic carcinoma. FNAC revealed hypercellular smears composed of plasma cells with eccentrically placed nuclei and perinuclear hoff. Hematological work up and other relevant investigations including urine for Bence Jones protein ruled out multiple myeloma or other plasma cell dyscrasias. Subsequent histopathological examination and IHC (immunohistochemistry) confirmed the diagnosis of primary plasmacytoma of thyroid. Discussion: EMP can present with elevated anti thyroid antibodies and can be associated with lymphocytic thyroiditis; however, in our patient these findings were not present.