A Rare Presentation of a Primary Mediastinal Large B Cell Lymphoma with Secondary Pancreatic Involvement Manifested as an Acute Pancreatitis

Abstract

Introduction: Primary mediastinal B cell lymphoma comprises of 6-10% of diffuse large B cell lymphoma (DLBCL) however, the incidence of pancreatic involvement is relatively rare. Primary pancreatic lymphoma or the secondary involvement of the pancreas from a primary lymphoma source can mimic cancer. Case Description: We report a case of a 51-year-old Caucasian male who initially presented to his PCP after having new onset of 3-4 episodes of loose stools for a couple of days followed by symptoms of abdominal bloating, early satiety and decreased appetite and was sent to the ED for acute pancreatitis after noted to have elevated lipase. His past medical history was negative for alcoholism, medication use or any family history of pancreatitis. CT chest revealed an anterior mediastinal mass 8.85 cm diameter x 12 cm L x 5.3 cm AP without any evidence of pericardial tamponade. CT abdomen revealed a 2.9 cm lobulated mass on the posterior margin of the head of the pancreas with ductal dilatation. The patient underwent a mediastinotomy with excion and biopsy of the anterior mass and adjacent nodes. The biopsy result revealed Primary Mediastinal (Thymic) large B cell lymphoma. EUS-FNA of the pancreatic mass revealed hypoechoeic mass with pancreatic duct dilatation and no regional lymph node involvement. Biopsies taken were compatible with lymphoma cells. Immunocytochemistry stain was strongly positive for CD 20 and PAX-5. During his hospitalization, the patient became jaundiced. RUQ US/Doppler revealed intra-hepatic and extra-hepatic ductal dilatation. ERCP with by biliary stenting of the CBD performed.with subsequently improvement of the LFTs. After 5 cycles of CHOP + Rituximab a repeat CT abdomen and a PET scan showed complete resolution of the mediastinal mass and lymphoma. Discussion: Primary mediastinal large B-cell lymphoma is a unique type of B-cell lymphoma. It constitutes 6-10% of all diffuse large B-cell lymphomas. Non-Hodgkin's Lymphoma is rarely considered in the differential diagnosis for patients presenting with obstructive jaundice as only 1-2% of adults with NHL have been shown to have biliary obstruction due to their malignancy. A literature search revealed that only two case of secondary pancreatic and mediastinal involvement by B-cell lymphoma presenting as acute pancreatitis has been published. Conclusion: This is the second case of large B-cell lymphoma presenting with concomitant primary pancreatic and mediastinal involvement. Diagnosis is based on cytological confirmation.