S3530 A Case of Extramedullary Plasmacytoma of the Head of the Pancreas

Introduction: The majority of patients with multiple myeloma (MM) present with signs or symptoms related to kidney damage from immunoglobulin deposition and infiltration of plasma cells into bone or other organs. Extramedullary plasmacytoma (EP), initially present in a minute percent of MM cases, involves the invasion of plasma cell tumors in organs outside the bone marrow. A small percent of patients with MM will later develop EP, which is often associated with inferior survival. We present a patient with IgG-Lambda multiple myeloma with documented EP to the right orbit who additionally was found to have extramedullary plasmacytoma of the head of the pancreas. Case Description/Methods: A 66-year-old woman with a past medical history significant for IgG-Lambda MM (on daratumumab) with rare ocular involvement presented for evaluation for Endoscopic ultrasound (EUS). Computed tomography imaging, ordered for diarrhea during a recent hospitalization, showed a pancreatic head mass measuring 2.3 × 2.7 cm. Labs were significant for chronic anemia, chronic thrombocytopenia, and elevated liver function tests with a hepatocellular pattern. A right upper quadrant ultrasound demonstrated a heterogenous mass in the pancreatic head measuring 4.6 × 3.0 × 3.1 cm with associated intrahepatic and extrahepatic biliary duct dilation. EUS was significant for an irregular, hypoechoic, isoechoic, and heterogenous mass in the pancreatic head measuring 35.7 mm by 32.8 mm in maximal cross-sectional diameter with poorly defined endosonographic borders. A fine needle biopsy was performed. Pathology showed pancreatic tissue with abundant plasma cells, compatible with recurrent-residual IgG Lambda-restricted multiple myeloma. In situ hybridization for kappa and Lambda performed revealed diffuse Lambda restriction with cells of interest showing strong diffuse positivity for IgG and were negative for IgG4. Discussion: Patients with MM often present with anemia, bone pain, elevated creatine, generalized weakness, fatigue, hypercalcemia, and weight loss. Rarely do patients present with signs or symptoms of extramedullary plasmacytoma. Additionally, pancreatic plasmocytoma is rare, with some sources citing only 50 documented cases. A more recent case report with a literature review in 2017 found only 63 cases from 1950 to June 2016. We aim to highlight the importance of gastroenterologists being vigilant when a pancreatic mass is found in a patient with both a history of MM and EP, as pancreatic plasmacytoma should be considered high on the differential.