Endocrine cells of transitional mucosa adjacent to colonic adenocarcinoma.

Transitional mucosa (TM) is used to describe mucosa adjacent to colonic adenocarcinoma with characteristic morphological and histochemical features. There is currently much debate about its aetiology. Some suspect it to be premalignant; others view it as a reactive change. Studies have looked at the morphology of TM and the type of mucins secreted by goblet cells within TM. Little work has been done on the third group of cells present in colonic mucosa; the enteroendocrine cells. These cells have many functions concerned predominantly with modulating the local environment. They are thought to be able to influence growth and metabolism. There is growing evidence in animal studies which suggest that hormones present within endocrine cells of colonic mucosa can influence colonic tumour growth rates. In this study endocrine cells stained with histochemical and immunocytochemical techniques were examined under the light microscope. Serotonin immunoreactive cells, the predominating endocrine cells of colonic epithelium, were present in greater numbers within the TM. Their increase was proportional to the increase in height of the mucosa of the TM. The increase was also proportional to the increase in epithelial cell numbers within the mucosa. This suggests that they proliferate together with the other epithelial cells of TM. In conclusion, serotonin containing cells appear to be an integral component of TM.