Newly-formed lymph nodes in the submucosa in chronic inflammatory bowel disease

Background and Aims: Routine diagnostic work revealed cell aggregates remin iscent of lymph nodes in the bowel submucosa in occasional cases of chronic inflammatory bowel disease. We therefore investigated whether they fulfill criteria for classification as lymph nodes. Methods: Colon with terminal ileum from a patient with florid Crohn's disea se and a colectomy specimen from a patient with ulcerative colitis were inv estigated. Sections were immunostained with antibodies that recognize endot helial and sinus-lining cells, immune-accessory cells, and lymphoid cells. Results: Circumscribed collections of cells that fulfill all the major crit eria for classification as lymph nodes were found in the large and small bo wel. They had marginal and intermediate sinuses (positive for BMA 120, CD34 , CD31, X-11, and von Willebrand's factor), afferent lymph vessels, T- and B-regions, and a capsule. Small collections composed predominantly of B cel ls that had only a marginal sinus were also occasionally observed. Conclusion: Secondary mucosa-associated lymphoid tissue, typically seen as follicular lymphoid hyperplasia, also appears to occur as secondary submuco sal lymph nodes. This phenomenon seems inconsistent with the notion that ly mph nodes do not develop after birth. We have also noted secondary developm ent of lymph nodes in lymphangioma and lymphangioleiomyomatosis. It is poss ible that local lymph vessel proliferation, possibly with chronic lymphedem a of the tissue involved is an important prerequisite for lymph node neogen esis.