The Oncological Characteristics of Colonic Polyps in Humans in View of Morphogenesis of Experimental Intestinal Tumors

A comparative study of the morphology and morphogenesis of intestinal epithelial tumors induced by treatment with 1, 2-dimethylhydrazine in over 2,000 rats and 1,415 polypoid lesions in the human colon and rectum was conducted. The development of experimental cancer starts with the expan-sion of the proliferative zone in intestinal crypts. The first cancer lesion to occur is carcinoma in situ which develops in the superficial layers of flat mucosa. Further evolution of carcinoma in situ with invasion within the lamina propria of the mucosa leads to superficial cancer development. Invasive cancer develops, when neoplastic structures extend into the sub-mucosal layer. Therefore, experimental intestinal adenocarcinoma appears denovo. Morphogenetic studies showed that the preinvasive stage of cancer may persist for a long time. In such cases, structural and cytologic signs of epithelial atypism and pleomorphism may be of vital importance for the detection of malignancy. Hence, when non-invasive polypoid lesions in hu-mans are checked for malignancy, emphasis should be placed on the detec-tion of the following morphologic manifestations of atypia : a considerabe decrease or complete absence of goblet cells, epithelial pseudostratification or even a multilayer structure, location of mitoses in the superficial areas of tumors and an increasing proportion of abnormal mitoses, appearance of papillary and villous structures and changes in their configuration, bizarre outlines of tumor glandules, cellular and nuclear polymorphism, appearance of cribriform structures, numerous plasma cells and karyorrhexis-affected lymphocytes in tumor stroma, etc. Invasion was detected in the dissected intestinal segments in 70% of the cases in which the said changes were observed in biopsy. No morphologic signs of malignancy was detected in adenomatous polyps. On the other hand, such early stages of adenocar-cinoma development as carcinoma in situ and superficial cancer at the back