[Precancerous lesions in the gastrointestinal tract].

In the large intestine, the pathologist has to differentiate between multiple polyps and polyposis (more than 100 polyps), further between adenomatosis (coli) and non-neoplastic (tumorlike) polyposis. Without prophylactic colectomy, in about 80% of adenomatosis patients an evolution of cancer is observed. Patients with extensive or total ulcerative colitis and a long history have an increased risk for developing carcinoma. Precancerous dysplasia can be demonstrated in rectoscopic and/or colonoscopic biopsies. Cancers complicating adenomatosis or ulcerative colitis account for only a very small proportion of large bowel carcinoma. The "adenoma-cancer sequence" is of greater importance. Colorectal polyps should be removed endoscopically whenever possible. Most gastric polyps are non-neoplastic and have no carcinomatous potential. The true adenoma and the so-called borderline lesion only can be considered as precursor of the gastric carcinoma.