Malignant Transformation of Perianal Fistulas: A Systematic Review of the Literature.

Malignant transformation of a perianal fistula is rare, predominantly associated with chronic fistula. Carcinogenesis is presumably initiated by chronic inflammation, and its mechanism is not clearly understood. We aimed to study the clinicopathologic characteristics and treatment outcomes of patients with malignant perianal fistula. A systematic literature search was performed on the electronic databases of PubMed, Scopus, and Web of Knowledge. A single-arm meta-analysis of non-comparative studies was performed using OpenMeta[Analyst] software. Eleven retrospective studies, including 172 patients (M: 135/F: 37), were included. The mean age of the patients was 56.89 years, and the most frequent presenting complaint was pain. The estimated mean duration of Crohn's disease (CD) was 30.61 years, and the mean duration of fistula before diagnosis was 17.92 years. The most commonly performed procedure was abdominoperineal resection (APR) and the most common histopathological subtype was adenocarcinoma. During the mean follow-up time of 40.56 months, 20.16% of patients had recurrence, and 35.62% of patients died. The pathophysiology of fistula-associated cancer is not well known, has diagnostic challenges, and the literature is sparse in predicting prognosis.