Patterns of Healing in the Appendix:The Morphologic Changes in Resolving Primary Acute Appendicitis and a Comparison With Crohn's Disease

We compared the histologic features of healing acute appendicitis (20 cases) with those of Crohn's disease at the appendix (54 cases), including the presence of granulomas, extrasubmucosal lymphoid aggregates, and subserosal fibrosis. Healing appendicitis assumed two basic patterns: the “usual” pattern, sometimes with an intraluminal cord of granulation tissue, and a xanthogranulomatous pattern. Epithelioid cell granulomas were seen exclusively in Crohn's disease (19/54; 35%). Furthermore, large numbers of lymphoid aggregates involving the muscularis propria or dense concentric subserosal fibrosis exceeding half the width of the muscularis propria in cross-section were signifi cantly associated with Crohn's disease. Xanthogranulomatous features were not seen in the Crohn's cases. The presence of granulomas, extrasubmucosal lymphoid aggre gates, and concentric subserosal fibrosis in an appendectomy specimen may suggest the diagnosis of Crohn's disease. Int J Surg Pathol 2(1):23-30, 1994