Aneurysmal Dilatation in Bowel Lymphoma

Primary gastrointestinal lymphoma classically presents with marked, bulky bowel wall thickening that paradoxically widens the bowel lumen—a phenomenon termed "aneurysmal dilatation."

This occurs because the lymphomatous infiltrate destroys the muscularis propria and the myenteric nerve plexus, which leads to a localized loss of autonomic tone and smooth muscle relaxation. Consequently, despite severe circumferential wall thickening, these tumors rarely cause true mechanical bowel obstruction.

This is a crucial diagnostic clue differentiating lymphoma from the constricting, scirrhous strictures typical of adenocarcinoma.