Granulomas without foreign body giant cells in perianal fistula tissue suggest Crohn's disease.

Objectives: Histopathological characteristics of granulomas in perianal fistula of patients with Crohn's disease (CD) remain unexplored. We aimed to assess the histopathological features of granulomas in perianal fistula in CD.

Methods: A retrospective analysis was conducted by reviewing the medical and pathological records of 4430 cases who underwent perianal fistulectomy at our hospital between June 2015 and June 2023. The patients were divided into the CD group, tuberculosis (TB), and non-CD group, respectively, based on their final diangosis. The detection rate of granulomas and differential histopathological features were investigated.

Results: Among the 4430 patients, granulomas were identified in 41 cases, including 25 had CD, 2 had pulmonary TB, and 14 only exhibiting perianal lesions with no other comorbidities. Additionally, there were altogether 93 CD cases, resulting in a detection rate of granuloma of 26.9%, which was considerably higher than that in the non-CD group (26.9% vs 0.3%, p < 0.001). The majority (85.7%) of the perianal fistula tissues in the non-CD group contained foreign body giant cells, while this was observed in only 1 (4.0%) out of the 25 cases with CD. We proposed that granulomas in the perianal fistula in the non-CD group were mostly foreign body granulomas. Moreover, granulomas in the non-CD group were larger than that of the CD group (1135 μm vs 519 μm, p < 0.001).

Conclusion: Most CD cases have less granulomas (≤3) and no foreign body giant cells. Ribbon-like granulomas can be seen only in CD cases.