S3307 Multiple Myeloma Relapse With Pancreatic Plasmacytomas: A Case Report

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Introduction: Extramedullary plasmacytomas (EMPs) are rare tumors of neoplastic plasma cells with minimal or no bone marrow involvement. They occur in ∼5% of multiple myeloma (MM) cases, often reflecting disease progression. EMPs typically affect the head, neck, or upper respiratory tract, while gastrointestinal involvement (including the pancreas) is rare, seen in ∼10% of cases. Pancreatic plasmacytomas may cause obstructive jaundice or abdominal pain. We present a unique case of MM relapse with 2 pancreatic plasmacytomas. Case Description/Methods: A 59-year-old woman with a history of MGUS, MM (status-post stem cell transplant in 2024, previously in remission), cervical cancer, and hypothyroidism presented with 1 week of nausea, epigastric/right upper quadrant pain, pale stools, and dark urine. Exam showed epigastric tenderness and purpura. Labs revealed hyperbilirubinemia (2.2 mg/dL), ALP 263 U/L, AST 533 U/L, ALT 1125 U/L, lipase 205 U/L, and total protein 8.5 g/dL. Computed tomography showed mild pancreatitis and gallbladder wall thickening without biliary dilation. Magnetic resonance imaging showed diffuse pancreatic enlargement with ill-defined nodular areas. Endoscopic ultrasound revealed 2 masses: a 3.5 cm lesion in the body and a 2.5 cm lesion in the head. Biopsy confirmed a kappa-restricted plasma cell neoplasm (CD81+, CD19-, CD20-, CD56-, CD117-, CD28-, CD27-). KCD chemotherapy (Carfilzomib, Cyclophosphamide, Dexamethasone) was initiated. Due to rising bilirubin and liver enzymes, endoscopic retrograde cholangiopancreatography (ERCP) was performed, revealing a distal common bile duct stricture; a stent was placed with rapid bile drainage. Three days later, the patient was re-admitted with post-ERCP pancreatitis, managed conservatively. PET showed decreased uptake in pancreatic lesions, and she transitioned to a 28-day regimen of daratumumab, carfilzomib, pomalidomide, and dexamethasone. Discussion: Pancreatic involvement in MM is extremely rare. This case is notable for 2 discrete plasmacytomas, including 1 in the body, an uncommon site. The presentation mimicked pancreatitis and biliary obstruction, emphasizing the diagnostic challenge. Endoscopic ultrasound with biopsy was critical, despite procedural risk. Complex management including chemotherapy, ERCP, and second-line agents led to clinical improvement. This case adds to the limited literature and underscores the importance of recognizing pancreatic EMPs in relapsed MM.

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