Carcinoma associated with anal fistula: A clinicopathologic study of 25 patients

Abstract

Purpose: Carcinoma associated with anal fistula is a relatively rare carcinoma that occurs when a chronic anal fistula becomes cancerous. We carried out a clinicopathologic study of carcinoma associated with anal fistula. Method: We analyzed the clinicopathologic features and treatment outcomes of 25 patients with carcinoma associated with anal fistula who were treated at our hospital between 1997 and 2014. Results: The mean age of the patients was 58 years (34-82 years), and the male to female ratio was 23 : 2. The median number of years between the onset of anal fistula and the onset of carcinoma was 12 (1-50 years). Seven patients had suffered from Crohn disease for a median of 23 years (12-29 years). The diagnosis of carcinoma associated with anal fistula was established by evaluation under lumbar anesthesia in 14 patients, endoscopic biopsy in 6, office biopsy (local anesthesia) in 3, mucus cytology in 1, and intraoperative biopsy in 1. Thirteen patients underwent repeated biopsy. Fourteen patients underwent abdominoperineal resection, 10 underwent total pelvic exenteration, and 1 underwent Hartmann's operation. Histologically, 68% of patients had mucinous adenocarcinoma and 40% had nodal involvement. Curative resection was performed in 18 of 25 patients. The 5-year overall survival rate was 45.8%. Survival was influenced significantly by curability (P<0.0001). We found no significant difference in clinicopathologic features between patients with or without Crohn disease. Conclusion: High clinical suspicion is crucial to avoid any delay in the diagnosis and treatment of carcinoma associated with anal fistula. Patients with long-term chronic anal fistula should focus on changes in or deterioration of the symptoms. Biopsy and cytology must be repeated if there are new findings that signal any possible malignant transformation. Aggressive excision with a clear margin is required for cure.