BACKGROUND : Patients with Crohn's disease (CD) are generally known to be at an increased risk of cancer. The anorectal area is the most frequent cancer site in Japanese CD patients. However, the risks are not well defined. The aim of this study was to clarify the clinicopathological characteristics of Japanese CD-associated anorectal carcinoma patients and to explore screening methods for the detection of cancer at earlier stages. METHODS : A systematic review of case series and reports of Japanese CD-associated anorectal cancer patients published between 1983 and 2016 was conducted. RESULTS : There were 144 cases of cancer arising from anorectal lesions of CD. The median duration from the onset of CD to the cancer diagnosis was approximately 17 (0-39) years. The most prevalent histological type of cancer was mucinous carcinoma (49.3%), and 82.1% of patients were over T3 invasion. There were only 15.6% cases with early stage disease. A total of 82% patients had enhanced symptoms, whereas 56.3% of the early cancer cases had no symptomatic changes. Approximately 90% of cases were diagnosed preoperatively, and almost all early cancer patients were diagnosed with colonoscopy. The 5-year overall survival rate was 35.8%. CONCLUSIONS : CD-associated anorectal carcinoma had a poor prognosis due to the advanced stage of the cases and aggressive histological features. As earlier-stage cancer is associated with a better prognosis than advanced stage disease, and it is also typically diagnosed by colonoscopy, surveillance colonoscopy may therefore help to improve the prognosis in cases without any symptomatic changes.