Relation of granulomas to lymphatic vessels in Crohn's disease

AIMS: To examine the relation between granulomas and lymphatic vessels in Crohn's disease. METHODS: Formalin fixed, paraffin wax embedded sections were selected from surgical resection specimens from 10 cases diagnosed as Crohn's disease. The block that showed the most granulomas was selected from each case. Sections 5 microns thick were immunostained with antibodies directed against the endothelial markers factor VIII related antigen and Ulex europaeus lectin, and against the vascular wall components collagen IV and laminin. Granulomas were counted on each slide in the serosa, muscularis propria, submucosa, and mucosa. In each area granulomas were classified according to their relation to lymphatic or blood vessels. RESULTS: Overall, an average of 46.1% of granulomas (range 15.3-90.4%) was related to lymphatic vessels, with the majority of these being adjacent to the vessel, rather than in the lumen or distorting the wall. A smaller percentage (10.1%, range 2.4-25.8%) was related to blood vessels. CONCLUSIONS: A significant proportion of granulomas in Crohn's disease is associated with lymphatic vessels. Blood vessel involvement may be a secondary phenomenon, rather than the primary event.