This article describes a patient with a severe relapse of newly diagnosed ulcerative colitis, with toxic megacolon, sclerosing cholangitis, and a Bauhin valve neuroendocrine neoplasm. The relationship between inflammatory diseases of the colon, cancer risk including neuroendocrine tumors, the potential impact of these tumors on the course of the underlying disease, and clinical differences between ulcerative colitis with and without coexisting sclerosing cholangitis are discussed based on the latest literature.