Surgical therapy for ulcerative colitis(UC) depends on the medical therapy administered for the patient’s condition. UC is a benign disease. However, it has been reported that the rare cases of cancer in UC patients are increasing, and such cases have a worse prognosis. Recently, surgical therapy has greatly changed, there has been quite an increase in the number of UC patients with high-grade dysplasia and/or cancer. These lesions are known as colitis-associated cancer(CAC). The relationship between inflammation and tumorigenesis is well-established, and in the last decade, a great deal of supporting evidence has been obtained from genetic, pharmacological, and epidemiological studies. Inflammatory bowel disease, especially UC, is an important risk factor for the development of colon cancer. We should determine the risk factors for UC patients with cancer based on a large body of data, and we should attempt to prevent the increase in the number of such patients using these newly identified risk factors in the near future. Actively introducing the surgical treatment in addition to medical treatment should be considered. Several physicians should analyze UC from their unique perspectives in order to establish new clinically relevant diagnostic and treatment methods in the future. This article discusses CAC, including its etiology, mechanism, diagnosis, and treatment in UC patients. Surgical therapy for ulcerative colitis (UC) depends on the medical therapy administered for the patient’s condition. However, it has been reported that the rare cases of cancer in UC patients are increasing, and such cases have a worse prognosis . Recently, surgical therapy has greatly changed, there has been quite an increase in the number of UC patients with high-grade dysplasia and / or cancer. These lesions are known as colitis-associated cancer (CAC). The relationship between inflammation and tumorigenesis is well-established, and in the last decade, a great deal of supporting evidence has been from genetic, pharmacological, and epidemiological studies. Inflammatory bowel disease, especially UC, is an important risk factor for the development of colon cancer. determine the risk factors for UC patients with cancer based on a large body of data, and we should attempt to prevent the increase in the number of such patients using these newly ident Actively introducing the surgical treatment in addition to medical treatment should be considered. Several physicians should analyze UC from their unique perspectives in order to establish new clinically relevant diagnostic and treatment methods in the future. This article discusses CAC , including its etiology, mechanism, diagnosis, and treatment in UC patients.