Proposal of novel staging system CNM (Crohn's primary site, nodes, mesentery) to predict postoperative recurrence of Crohn's disease

After oncologic resection, histological grading and staging of the tumor give important prognostic information about the future risk of recurrence and hence influence the subsequent management plan. Several studies and their meta-analysis have shown that various histological features (e.g., microscopic positive resection margins, plexitis, granuloma, mesenteric inflammatory activity) can predict postoperative clinical/endoscopic/surgical recurrence after resection in Crohn's disease (CD). Inclusion of mesentery in surgical resection specimens has been shown to reduce surgical recurrence after ileocolonic resection in CD. However, there is no uniform histopathological staging system for risk stratification in postoperative CD to systematically predict postoperative recurrence. This is because the prediction to date is based on clinical characteristics (smoking status, disease phenotype, surgical history). Histopathological predictors are still not adopted in routine clinical practice due to the lack of a uniform staging system, heterogeneity of published studies and lack of standardized definition of histological features. In this article, we attempted to incorporate all such histological features in a single histological staging system CNM (Crohn's primary site [resection margin positivity, plexitis, granuloma, depth of infiltration], nodes [presence of granuloma], mesentery [involved or not]) in surgical resection specimen in CD. The proposed CNM classification would help to enable systematic reporting, design future clinical trials, stratify postoperative recurrence risk and choose appropriate postoperative prophylaxis.