Diffuse large B-cell lymphoma as a rare cause of small bowel obstruction: case report and literature review.

Introduction: Diffuse large B-cell lymphoma (DLBCL) is the most frequent subtype of non-Hodgkin lymphoma, representing about 30% of cases. Extranodal involvement occurs in 10-20%, most commonly in the stomach. Small bowel localization is less frequent and can occasionally present as small bowel obstruction (SBO), a challenging and unusual initial manifestation. Case Presentation: A 65-year-old woman with no relevant medical history was admitted for acute abdominal pain, vomiting, and distension evolving for 48 h. Clinical examination showed abdominal tympany with no palpable masses and normal laboratory tests. Abdominal computed tomography revealed marked small bowel dilatation with a thickened, stenosing ileal segment. Conservative treatment was initiated, but persistent symptoms prompted surgery. Exploratory laparotomy revealed a 4 cm ileal lesion located 3 m from the duodenojejunal junction. Segmental resection and side-to-side mechanical anastomosis were performed. Histopathology showed a transmural proliferation of large atypical lymphoid cells. Immunohistochemistry demonstrated CD20 positivity and negativity for CD10 and Bcl-6, confirming a diagnosis of non-germinal center DLBCL. The postoperative course was uneventful and the patient remained disease-free at 8-month follow-up after completing R-CHOP chemotherapy. Discussion: DLBCL of the small intestine may mimic common causes of SBO, delaying diagnosis. Cross-sectional imaging is helpful to identify the obstruction, but histological examination remains essential. Surgical resection is crucial both for symptom control and for establishing the diagnosis, after which systemic chemotherapy, usually R-CHOP, is indicated. Conclusion: Although rare, DLBCL should be considered as a differential diagnosis in unexplained SBO. Early recognition and a multidisciplinary management strategy improve prognosis.