cancer colorectal adenocarcinoma A malignant tumor usually arising from the epithelium lining the large intestinal mucosa. Colon carcinoma is one of the most common malignancies in both males and females, and is especially common in North America and Europe. Grossly, most colon carcinomas are polypoid or ulcerating lesions. Microscopically, adenocarcinoma is the most frequently seen morphologic subtype. Prognosis depends on the stage of the disease (depth of invasion, metastasis to regional/distal lymph nodes or other anatomic sites). -- 2004 An adenocarcinoma arising from the colon. It is more frequently seen in populations with a Western type diet and in patients with a history of chronic inflammatory bowel disease. Signs and symptoms include intestinal bleeding, anemia, and change in bowel habits. According to the degree of cellular differentiation, colonic adenocarcinomas are divided into well differentiated, moderately, and poorly differentiated. Morphologic variants include the mucinous adenocarcinoma and signet-ring adenocarcinoma. Lymphatic or hematogenous spread can occur early in the process and lead to systemic disease. Tumors or cancer of the COLON or the RECTUM or both. Risk factors for colorectal cancer include chronic ULCERATIVE COLITIS; FAMILIAL POLYPOSIS COLI; exposure to ASBESTOS; and irradiation of the CERVIX UTERI.