Galle/Pankreassekret und colorectales Carcinom im Tierexperiment

Changes in intestinal mucosa above lymph follicles during carcinogenesis in rats. A light and electron microscopic study

Changes in the intestinal mucosa during carcinogenesis were investigated in 36 rats after weekly s.c. injection of 20 mg dimethylhydrazine/kg bodyweight. More changes were seen in the large than in the small intestine. In the first week, 60% of colonic lymphoid plaques displayed various crypt abscesses and glandular regenerations. These mucosal changes correspond to the glands covering the lymph follicles, in direct contact with lymphoid cells. Beginning in week 8, dysplastic glands developed in these mucosal areas above the lymph follicles. The number of lymphoid plaques with dysplastic glands in the large intestine increased week by week, attaining 75% in week 20. At the end of week 12 the first adenocarcinoma was detected in the cecum by light microscopy, and classified as a poorly differentiated adenocarcinoma with signet ring cells infiltrating the lymph follicles which contained endocrine cells. The majority of adenocarcinomas (10 cases) occurred in week 20. Of these, 7 were localized above the lymphatic plaques in the intestine. Endocrine cells were found in varying numbers in 6 of 10 adenocarcinomas. Three endocrine cell carcinomas, corresponding to human adenocarcinoids or goblet cell carcinoids, developed within the intestinal mucosa; all were identified as poorly differentiated intestinal adenocarcinomas, two of them situated above lymph follicles. These suprafollicular tumors developing from the glandular base, were composed of mucoid cells, endocrine cells, and undifferentiated cells. Microcarcinomas are considered as initial stages of endocrine cell carcinoma.

What's new in colon carcinogenesis?

Among precancerous conditions in the colon and rectum, adenomas are the most important, paradigmatically so in adenomatosis coli, a genetic predisposition of autosomal dominant type. Statistical relevance is also attributed to long-term ulcerative colitis, Morbus Crohn, and Gardner's syndrome. Dietary factors seem to play an essential role. Highly developed countries in Western Europe and North America whose prevalence rates of colorectal carcinoma are highest, also have a particularly high daily intake of fat and meat. The proportion of fibers in a diet shows an inverted correlation with the prevalence of colorectal carcinoma. Many epidemiologic data are still rather inconsistent and in some cases rather weak. Detailed case-control studies are needed to substantiate the general statement: Our life style, especially our daily food, is obviously related to the rise of colorectal carcinoma.