An Intestinal Intravascular Large B-Cell Lymphoma Presenting as Small Bowel Ischemia: A Case Report and Literature Review.

Intravascular large B-cell lymphoma (IVLBCL) is a rare type of malignant lymphoma characterized by the proliferation of neoplastic cells within small blood vessels. Here, we present a rare case of small intestinal IVLBCL presenting with intestinal necrosis. A 78-year-old man presented with vomiting and abdominal pain. Contrast-enhanced CT revealed an edematous, poorly enhanced small intestine, suggestive of ischemia. Emergency laparoscopy was performed based on radiological findings indicating intestinal ischemia, and a 50 cm segment of necrotic ileum was identified. This segment was resected with adequate margins and reconstructed using an end-to-end anastomosis. Embolic material was noted in the mesenteric vessels. Histopathological examination revealed large, uniform lymphoid cells within vascular lumina and lymph node sinuses. Additional immunohistochemical analysis showed positivity for CD20 and Ki-67 (80-90%), consistent with high-grade IVLBCL. The patient was transferred to the hematology department to initiate chemotherapy with the R-CHOP regimen. IVLBCL often lacks typical physical features, such as lymphadenopathy or mass formation, making diagnosis difficult. Intestinal IVLBCL, a rare malignant lymphoma characterized by the selective proliferation of tumor cells within the lumen of small- to medium-sized blood vessels, represents a GI manifestation of IVLBCL. This case report describes a 78-year-old man who presented with vomiting and abdominal pain and was diagnosed with IVLBCL.