S6406 Incidental Finding of H. pylori-Negative MALT Lymphoma Following Positive Cologuard Screening

Introduction: H. pylori-negative mucosa-associated lymphoid tissue (MALT) lymphoma is a rare and challenging diagnosis, especially in asymptomatic patients. We present an unusual case of incidentally discovered H. pylori-negative MALT lymphoma during a positive Cologuard workup in a patient without upper gastrointestinal symptoms. Case Description/Methods: A 63-year-old White obese man with type II diabetes, gastroesophageal reflux disease (GERD), and chronic smoking, presented to the gastroenterology clinic after a routine positive Cologuard test. He reported daily bowel habits, but experienced intermittent constipation and occasional rectal bleeding attributed to a history of hemorrhoids. He denied abdominal pain, nausea, vomiting, unintentional weight loss, or other symptoms. He had never undergone a colonoscopy or an upper endoscopy. Given his risk factors – chronic GERD, obesity, smoking, and unspecified family history of cancer, both colonoscopy and esophagogastroduodenoscopy (EGD) were performed. EGD showed a 5 mm salmon-colored island proximal to the Z-line, biopsied, consistent with Barrett’s esophagus. A separate 15 mm area of irregular mucosa was visualized in the gastric antrum, biopsied, and showed chronic active gastritis with lymphoepithelial proliferation and atypical lymphoid aggregates. Immunohistochemistry demonstrated B cell phenotype (CD20/PAX5 positive) with abnormal BCL-2, CD43, and MNDA expression, negative for CD10 and cyclin D, and low proliferative index. H. pylori was negative. Overall, morphonology and immunophenotype were consistent with H. pylori-negative MALT lymphoma. Oncology was consulted and recommended a staging PET computed tomography (CT), which showed increased fluorodeoxyglucose (FDG) uptake in gastric body and antropyloric region of the stomach. Patient is arranged for oncology follow-up for further management. Discussion: H. pylori-negative MALT lymphoma is uncommon, less responsive to antibiotic therapy, and often requires radiation and systemic treatment, depending on the initial stage at diagnosis. Our patient, despite being asymptomatic, had overlapping risk factors such as chronic smoking, obesity, and an unspecified family history of cancer, which may have contributed to pathogenesis. This case highlights the importance of comprehensive gastrointestinal evaluation in colorectal cancer screening patients, particularly when risk factors warrant concurrent upper endoscopy.