Endoscopic ultrasound-fine needle aspiration: A novel way to diagnose a solitary extramedullary plasmacytoma of the liver

Plasmacytoma is a neoplastic production of a single line of plasma cells, usually forming monoclonal immunoglobulin. It most often occurs in the bone marrow; however, in 3% of the cases, solitary extramedullary plasmacytoma arises, which is a proliferation in the soft tissue, outside the bone marrow. In only 10% of the cases is the gastrointestinal tract involved. A 77-year-old female presented with lethargy, abdominal fullness, bilious vomiting, and clay-colored stools. The patient was anemic with initial laboratory results showing increased total and direct bilirubin with elevated transaminases. Despite conservative management, liver function tests (LFTs) continued to increase. On endoscopic ultrasound (EUS), there was mild diffuse mucosal thickening consistent with possible infiltrative disease of the gastric body without any obvious focal lesions. There was a 1.7 cm × 1.8 cm hypoechoic heterogeneous lesion noted in the porta hepatis and fine needle aspiration (FNA) was performed. Cytology showed infiltrative plasma cells. The patient was then taken for computed tomography (CT)-guided biopsy of the liver. Pathology showed liver involvement by atypical plasma cells in a nodular and sinusoidal pattern. Immunohistochemical staining appropriately identified the solitary extramedullary plasmacytoma. Plasma cell neoplasm is essentially a clonal disease of differentiated B-cells that can encompass a broad spectrum and present as asymptomatic monoclonal gammopathy of undetermined significance to plasma cell neoplasms or multiple myeloma. Five percent of patients with multiple myelomas are diagnosed with extramedullary plasmacytomas, and even less than that are diagnosed as a primary lesion. When the liver is affected, either as a direct diffuse neoplastic plasma cell infiltration, or as a single or multiple space occupying lesion as plasmacytomas, symptomatic features include extrahepatic biliary obstruction, jaundice, or ascites. In our case, the patient was diagnosed via EUS-guided FNA (EUS-FNA) bringing to light an alternative method to its diagnosis.