Florid reactive lymphoid hyperplasia of the terminal ileum in adults: a condition bearing a close resemblance to low-grade malignant lymphoma.

Five cases of florid lymphoid hyperplasia of the ileocaecal region are described. This condition is characterized by large reactive germinal centres and a diffuse infiltrate of lymphoid cells and eosinophils which extends through the muscularis propria. There is a close resemblance to low-grade malignant lymphoma from which it can be distinguished only by the use of immunocytochemistry for light-chains. Using this technique it should be possible to classify all such lymphoid proliferations as either reactive or neoplastic and to eliminate ambiguous labels like pseudolymphoma.