Extramedullary plasmacytoma of the gallbladder diagnosed by endoscopic ultrasound fine needle aspiration (EUS-FNA).

Extramedullary plasmacytoma (EMP) is a rare entity that can exist independently or in conjunction with underlying plasma cell myeloma (PCM). When there is underlying multiple myeloma, the presence of EMP portends a poor prognosis. The most common locations for an EMP include the gastrointestinal tract, pleura, testis, skin, peritoneum, liver, endocrine glands and lymph nodes; involvement of the gallbladder is exceedingly rare with only five other cases reported and only one of which was associated with PCM. EMP of the gallbladder can manifest as acute cholecystitis, biliary obstruction, or may be asymptomatic. Treatment is traditionally surgical resection plus adjuvant chemotherapy or autologous stem cell transplant. We present a case of a 53-year-old man with PCM who was found to have a gallbladder mass on imaging and underwent endoscopic ultrasound (EUS) guided fine needle aspiration (FNA) of the mass, which was diagnostic of a plasma cell neoplasm.