With advances in the treatment of Crohn's disease (CD), the number of long-term cases is increasing, along with the incidence of CD-related cancers. Here, we discuss the clinical features, diagnosis, treatment, prognosis, and surveillance of CD-related cancers. There are regional differences in the common sites and histological types of CD-related cancers, with right-sided colon cancer accounting for 40% of cases in Europe and the US, and squamous cell carcinoma being common. In Japan, rectal and anal cancers account for 80% of cases, and mucinous carcinoma is common. The prognosis of CD-associated colon cancer and sporadic colon cancer is the same
however, the prognosis of CD-associated rectal cancer is clearly worse than that of sporadic rectal cancer. Early diagnosis is important to improve the prognosis of CD-associated rectal cancer, and it is necessary to establish a surveillance method for CD-associated cancer that combines colonoscopy, anesthetic proctoscopy, and imaging, as appropriate. The basic treatment for CD-related cancer is surgical resection
however, the criteria for selecting the surgical procedure are unclear, and there is no clear evidence for multidisciplinary perioperative treatment including chemotherapy and radiotherapy. Additionally, CD-related rectal and anal cancers have a higher local recurrence rate than that of sporadic rectal cancers
therefore, thorough local control is important. Furthermore, CD-related cancers have different epidemiologies in different regions
therefore, unique diagnostic and treatment strategies must be established for each region.