Recurrent Acute Pancreatitis Revealing Pancreatic Infiltration by CD20-Positive B-cell Lymphoma: A Diagnostic Pitfall in Extranodal Lymphoma

Acute pancreatitis most commonly results from gallstone disease, alcohol use, metabolic abnormalities, or medication effects. Malignant infiltration of the pancreas is a rare cause of pancreatic inflammation and may present with symptoms indistinguishable from more typical forms of pancreatitis. Pancreatic involvement by lymphoma is particularly uncommon and may mimic pancreatic neoplasms or recurrent inflammatory pancreatic disease. We present the case of a 29-year-old woman with a recently diagnosed CD-20-positive B-cell lymphoma who developed recurrent severe abdominal pain and markedly elevated pancreatic enzymes shortly after hospitalization for acute pancreatitis. Imaging revealed bulky retroperitoneal lymphadenopathy, bilateral renal enlargement, biliary ductal dilatation, and findings suspicious for pancreatic head involvement. Histopathologic evaluation of a retroperitoneal lymph node biopsy confirmed CD20-positive B-cell lymphoma. The patient underwent placement of a chemotherapy port and initiation of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), with subsequent clinical improvement. This case highlights pancreatic infiltration by lymphoma as a rare cause of recurrent pancreatitis and underscores the importance of considering hematologic malignancy in patients presenting with atypical pancreatic inflammation or unexplained lymphadenopathy.