Utility of Fine Needle Aspiration for Diagnosis of Plasmacytoma

Abstract

Plasmacytomas are rare extramedullary plasma cell neoplasms that present in bone and/or soft tissue. Diagnosis can require a variety of laboratory approaches such as serum protein electrophoresis, bone marrow biopsy, Bence Jones protein assays, and imaging. However, few case reports describe using fine needle aspiration for diagnosis. We present a case of a plasmacytoma diagnosis in a 55-year-old patient, who initially presented to the emergency room with symptoms of chest pain. Imaging revealed right apical and medial lung mass extending just posterior to the trachea with invasion and destruction of the anterolateral T3 vertebral body. Multiple smaller hypodensities were also present in thoracic vertebral bodies, ribs, and sternum. Biopsies were performed on the mediastinal mass. Fine needle aspiration revealed groups of mature and immature plasma cells at various stages of maturation. Flow cytometry demonstrated a kappa light chain-restricted plasma cell population. Paraffin immunoperoxidase studies showed that the neoplastic cells bore monotypic kappa light chains. The patient's presentation emphasizes the utility of fine needle aspiration, in conjunction with other ancillary studies, for diagnosing plasmacytomas.