S3345 Not Just Bone Deep: A Pancreatic Presentation of Myeloma – A Case Report and Review of the Literature

Introduction: Metastatic tumors to the pancreas primarily include breast, lung, ovarian, and renal cell carcinoma. Extramedullary involvement in hematologic plasma cell malignancies is rare and indicates a poor prognosis. We describe a rare case of extramedullary relapsing IgG Kappa multiple myeloma metastatic to the pancreatic body. Case Description/Methods: A 57-year-old man with IgG Kappa multiple myeloma (diagnosed 5 years prior, status post autologous stem cell transplant complicated by relapse of the disease 4 years later) presented to the emergency department due to a 3-day history of worsening left-sided abdominal and back pain. Relapsing disease was diagnosed in 2024 via a pathologic right humerus fracture while on lenalidomide maintenance therapy. He received 4 cycles of iberdomide, daratumumab, carfilzomib, and dexamethasone (Iber-KDd) as part of a clinical trial prior to his ED visit. On admission, his labs were notable for hemoglobin 11.8, platelets 409, lactate 2.7, and lipase 71, with a normal bilirubin of 0.5 and alkaline phosphatase of 71. Two days prior, he underwent a PET scan to evaluate a palpable mass in the left mid-back, which showed new fluorodeoxyglucose (FDG) avid abdominopelvic lymph nodes/implants and a new fluorodeoxyglucose avid pancreatic body lesion. In the ED, an abdominal computed tomography scan demonstrated a homogenous density in the pancreas without focal lesions or main ductal dilatation. Endoscopic ultrasound (EUS) found an 18 × 17 mm hypoechoic, heterogeneous mass in the pancreatic body with ill-defined borders. Fine needle biopsy (FNB) results demonstrated a kappa-restricted plasma cell neoplasm involving pancreas parenchyma. Prior to discharge, he started dexamethasone, cyclophosphamide, etoposide, and cisplatin (DCEP) with the plan to bridge to CAR-T therapy and to start palliative radiation therapy as an outpatient. Discussion: This case demonstrates extramedullary involvement of relapsing multiple myeloma in the pancreatic body without physical signs or laboratory findings of obstructive jaundice. In our literature review, pancreatic involvement in multiple myeloma is considered a rare entity that presents typically with signs of obstructive jaundice and indicates a poor prognosis, remaining a unique subtype of metastatic tumors to the pancreas. We highlight the diagnostic utility of an EUS-guided FNB when evaluating FDG-avid lesions on PET-computed tomography with the possibility of appropriate diagnosis to minimize delays in care and reduce morbidity and mortality.