FROM THE ARCHIVES OF THE AFIP - COLORECTAL ADENOCARCINOMA - RADIOLOGIC-PATHOLOGICAL CORRELATION

Colorectal adenocarcinoma is extremely common and the second most common cause of cancer death in the United States. Almost all colorectal adenocarcinomas arise from tubular and villous adenomas, most likely those greater than 2 cm in size. Occasionally, however, carcinoma will arise from areas of dysplasia of flat mucosa as in the case of inflammatory bowel disease. The annular constricting lesion, the most common appearance of adenocarcinoma in the left side of the colon, is caused by circumferential spread of tumor within the lymphatics of the inner circular layer of the muscularis propria. Fungating masses, manifesting with anemia or intussusception, are the most common appearance of adenocarcinoma in the right side of the colon. Saddle lesions, ulcerating masses, and infiltration tumors are less common forms of growth. Mucinous adenocarcinoma may be recognized rarely by calcification and more commonly by the low attenuation of excessive pools of extracellular mucin within the tumor. The degree of local spread and presence of lymphatic or hematogenous metastases are best classified by the TNM system, although the modified Dukes classification is frequently employed. Local disease is probably best assessed with endoscopic ultrasound. Cross-sectional imaging is most useful in the evaluation of advanced disease, recurrent disease, and associated complications, although the role of magnetic resonance imaging may expand with the introduction of endorectal coils. Screening programs for adenomas and early carcinomas have the potential to decrease the mortality from this malignancy with appropriate removal of adenomas. The radiologist, with use of barium enema studies, should be instrumental in initiating, participating in, and popularizing screening protocols for colon cancer.