Morphology and morphogenesis of experimental epithelial tumours of the intestine

SUMMARY-In a morphogenetic study of experimental tumors of the intestine, 556 male noninbred albino rats were given weekly sc injections of 21 mg 1,2-dimethyl-hydrazine dihydrochloridejkg body weight and were killed at ditferent intervals (10-70 ratsjwk) after the beginning of treatment. Intestinal carcinomas developed in almost all rats surviving 5 months after the beginmng of the ex-periment. In addition, intestinal tumors induced in 800 rats of both sexes were examined. Tumor development began with a widening of the proliferative zone within the crypts, an indication of enterocyte differentiation dis-orders. The ensuing in situ carcinoma became superficial cancer capable of invading the lamina propria of the mucosa. Its continued growth caused the tumor to pene-trate the tunica muscularis mucosae into the underlyin