Primary Plasmacytoma of Thyroid Gland Diagnosed by FNA Cytology: A Case Report

Introduction: Extramedullary plasmacytomas (EMPs) can arise from organs other than bones. The majority of EMPs occur in the upper respiratory tract. The thyroid gland is a rare site for EMPs. Case Presentation: We report a case of primary plasmacytoma of the thyroid in a 42-year-old man who referred to the outpatient clinic of Namazi Hospital, a governmental hospital affiliated to the Shiraz University of Medical Sciences, Shiraz, Iran, in January 2018. The diagnosis of plasmacytoma was made by fine-needle aspiration of thyroid. Conclusions: Primary plasmacytoma of the thyroid is a rare disease and its diagnosis can be made by cytology or pathology after ruling out benign conditions like Hashimoto thyroiditis by an appropriate workup. The prognosis of this disease is favorable, but the clinical follow-up of patients is mandatory because it can progress to multiple myeloma in some cases.