S3596 Beyond Inflammation: An Unexpected Lymphomatous Surprise in Pancreas

Introduction: Primary pancreatic lymphoma represents a rare pathological entity, accounting for less than 2% of extranodal non-Hodgkin's lymphomas. Its presentation as acute necrotizing pancreatitis is extremely rare and further underscores diagnostic complexity requiring high index of suspicion and potential for clinical misinterpretation. Case Description/Methods: A 23-year-old woman presented with 20-day history of severe epigastric pain radiating to back, accompanied by progressive abdominal distension. There were no typical pancreatitis triggers like cholelithiasis, drugs, trauma or alcohol. On examination, tenderness and palpable mass were present in epigastrium. Laboratory investigations revealed mildly elevated serum amylase and serum lipase. Sonography revealed a large thick walled collection in region of pancreas with no gall stones or biliary obstruction. Magnetic resonance imaging revealed nodular, thick walled loculated T2-hyperintense fluid collection replacing a large part of the pancreas; integrity of main pancreatic duct appeared disrupted. Based on clinical and imaging findings, a diagnosis of acute necrotising pancreas with large collection and possible duct disconnection was considered. The patient was treated conservatively and discharged. The patient was readmitted with worsening of pain abdomen after 1 month. Subsequent contrast-enhanced computed tomography (CECT) imaging revealed confluent necrotic pancreatic masses replacing the previously visualised collection and progressive abdominal lymphadenopathy. Percutaneous biopsy of retroperitoneal lymph node revealed sheets of large lymphoid cells exhibiting pleomorphism with cytoplasmic clearing. Immunohistochemistry (IHC) showed CD45 positivity in neoplastic lymphoid cells with 90% MIB-1 proliferation index. The neoplastic large lymphoid cells also showed CD20 diffuse membranous positivity with CD3 negativity, thereby confirming diagnosis of non-Hodgkin lymphoma. Discussion: Primary pancreatic lymphoma presenting as acute pancreatitis is an infrequent presentation and can be a clinical and imaging dilemma. Pancreatic lymphoma should be considered in differential diagnosis of patients presenting with acute pancreatitis with no obvious common etiologies. This case of acute pancreatitis highlights critical diagnostic considerations that lymphoma can mimic acute pancreatitis; persistent symptoms without clear etiology warrant extensive investigation and IHC analysis of biopsy for accurate diagnosis.