S3930 A Rare Case of Colonic MALT Lymphoma Presenting as Diffuse Colonic Nodularity

Introduction: Colonic mucosa associated lymphoid tissue (MALT) lymphoma is a rare subtype of extra nodal marginal zone lymphoma, commonly arising from mucosa-associated lymphoid tissue and accounts for less than 0.5 of colonic malignancies. While common in the stomach, it can affect other parts of the gastrointestinal tract. Colonic MALT lymphoma is thought to involve chronic inflammation, as seen with Helicobacter pylori in gastric MALT, and some cases were seen in patients with inflammatory bowel diseases. Patients typically present with nonspecific symptoms such as abdominal pain, lower Gastrointestinal hemorrhage, or changes in bowel habits. In some cases, the diagnosis is incidental, during routine colonoscopy. Endoscopic findings may show masses, polyps and ulceration. While rare, the incidence of this lymphoma is increasing, suggesting the need for awareness among clinicians. Case Description/Methods: A 69-year-old man with a history of alcohol use disorder, presented with new-onset abdominal pain. Lab work showed leukocytosis (white blood cell count of 27k), with 72% lymphocytes. A computed tomography (CT) scan performed revealed splenomegaly and prominent abdominal adenopathy. Peripheral blood flow cytometry confirmed clonal lymphocytosis. A bone marrow biopsy chronic lymphocytic leukemia (CLL), and “watch and wait” strategy was implemented. Then, patient returned a year later with weight loss, and worsening abdominal pain. Lab work revealed a hemoglobin level of 10.9 g/dL (previously normal), and occult blood was positive. Colonoscopy revealed extensive nodular, infiltrative lesions throughout the colon. Biopsies confirmed the diagnosis of marginal zone lymphoma. Due to the progressive nature of the lymphoproliferative process, the patient was initiated therapy with Acalabrutinib. However, the patient has experienced more pain in the enlarged nodal areas and has not experienced relief from abdominal pain. Then, another bone marrow biopsy was done showing transformation into diffuse large B cell lymphoma. Discussion: Our case depicts a rare presentation of colonic MALT lymphoma, manifesting as extensive nodularity involving almost the entire colon. Such a diffuse presentation is atypical, as previously reported cases in literature described colonic MALT lymphoma presenting localized polyps or ulceration. What supports the unique nature of this case is that the patient did not have the usual risk factors commonly associated with MALT lymphoma, such as H. pylori infection or inflammatory bowel disease.