What is the estimated incidence of squamous cell carcinoma arising in chronic perianal fistulae

What is known

- A systematic review found the incidence rate of SCC related to perianal fistula in Crohn's disease was very low (<1%), with poor prognosis. ¹ - Patients with perianal Crohn's disease are reported to have a 0.7% incidence of carcinoma. ¹ - Overall incidence of anal fistula-related cancers (SCC and adenocarcinoma) is reported at 0.3%–0.7%; fistula-associated SCC specifically is described as extremely rare. ²

What is unknown / caveats

- Most data are single case reports or small series, not incidence cohorts - 0.7% figure conflates SCC with adenocarcinoma in some sources - Precise SCC-specific incidence is not well established; reported figures are pooled estimates from sparse literature.

## References

1. Kotsafti A, Scarpa M, Angriman I, Castagliuolo I, Caruso A. Fistula-Related Cancer in Crohn's Disease: A Systematic Review. Cancers (Basel). 2021;13(6). PMID: 33809997.

2. PMID: 41114353. (metadata not in corpus)

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