Diffuse large B-cell lymphoma involving terminal ileum. The lymphoma cells diffusely infiltrate in between the normal glandular structures causing wide separation between them and distorting native architecture. There may be total flattening of the surface mucosa with disappearance of villous architecture. A small proportion of cases show an associated component of MALT lymphoma. The morphologic, immunophenotypic, and genotypic features of small intestinal DLBCL are similar to those of gastric DLBCL (images 33-44).