Introduction: Malignant transformation of perineal fistula in Crohn's disease has rarely been reported. The aim of this study is to define the patient's characteristics and clinical presentation of this rare disease. Methods: A systematic review of case series and reports published in English language between 1950 and 2008 was conducted. All cases with malignancy in low pelvic/perineal fistula in patients with Crohn's disease were included. All selected cases were then analyzed with respect to age, gender, duration of Crohn's disease and fistula, location of fistula, presenting symptoms, method of diagnosis, delay in diagnosis, histopathology, treatment, and outcome. Data analyses were done using chi-squared or Fisher's exact test and the Mann-Whitney test. Results: Literature review revealed 61 cases of carcinomas arising in perineal fistulas in Crohn's disease. Sixty-one percent (37) of the patients were females. Females were significantly younger than males at the time of diagnosis of cancer (47 vs. 53 years, P<0.032). Males were also noted to have significantly longer duration of Crohn's disease compared to females (24 vs. 18 years, P=0.005). However, females were noted to have the fistula for significantly shorter duration prior to cancer transformation when compared to males (8.3 vs. 16 years, P=0.0035). On initial examination, malignancy was suspected and proven only in 20% of patients (n=12). Adenocarcinoma was the most common histology (59%, n=36), followed by squamous cell carcinoma (31%, n=19). In most patients (59%, n = 36), the fistula was rectal in origin. Conclusions: A high suspicion for malignancy in chronic perineal fistulas associated with Crohn's disease should be maintained in spite of negative biopsies. Especially in women, the shorter duration of Crohn's fistulas prior to malignant degeneration necessitates an aggressive approach to rule out cancer.
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