Clinical significance of complement as a biomarker of disease activity in 4 cases of IgG4-related disease with retroperitoneal fibrosis.

UNLABELLED: Primary lymphoma of the ampulla of Vater is an exceptionally rare entity that may clinically mimic more common periampullary malignancies. Duodenal involvement is uncommon among gastrointestinal lymphomas, and mucosa-associated lymphoid tissue (MALT) lymphoma at this site is particularly rare. Diagnosis is often challenging due to the submucosal location of the lesion and the limited yield of conventional endoscopic biopsies. A 59-year-old woman presented with painless obstructive jaundice, weight loss and cholestatic liver enzyme abnormalities. Abdominal computed tomography (CT) scan revealed a periampullary mass with regional lymphadenopathy, biliary dilatation and a solitary lesion in the left hepatic lobe. Endoscopic retrograde cholangiopancreatography demonstrated a deformed ampulla with ulcerated periampullary mucosa. However, repeated endoscopic biopsies were inconclusive. Definite diagnosis was established only after endoscopic ultrasound-guided fine needle biopsy (EUS-FNB) of both the primary duodenal lesion and the hepatic lesion, which demonstrated B-cell non-Hodgkin lymphoma with immunohistochemical features consistent with MALT lymphoma. Staging investigations, including positron emission tomography-CT and bone marrow biopsy, showed stage IV disease. Ampullary MALT lymphoma is an extremely rare cause of obstructive jaundice and may be indistinguishable from other ampullary or pancreatic neoplasms. This case highlights the diagnostic limitations of conventional endoscopic biopsies and the pivotal role of EUS-FNB in obtaining adequate tissue samples from deeper layers. Early and accurate diagnosis is essential, as appropriate treatment can result in excellent clinical outcomes. EUS-FNB should be considered when initial biopsies are nondiagnostic in suspected periampullary malignancies, as it may facilitate the diagnosis of rare entities such as MALT lymphoma.

LEARNING POINTS: MALT lymphoma is a rare subtype of non-Hodgkin lymphoma, and involvement of the ampulla of Vater is exceptionally uncommon.Obstructive jaundice is the most common clinical presentation of ampullary lymphoma.Endoscopic ultrasound-guided tissue acquisition is particularly valuable when conventional endoscopic biopsies are nondiagnostic.