Morphogenesis of colonic adenomas in mice treated with N,N'-dimethylhydrazine dihydrochloride.

The morphogenesis of colonic adenomas in ICR mice treated with N,N'-dimethylhydrazine dihydrochloride (DMH) was studied. Treatment of 17 mice with DMH (20 mg/kg/week) for 24 weeks induced 100% incidence of multiple adenomas in the mucosa of the most distal 7 cm of the large intestine. These adenomas were composed of atypical epithelium of the absorptive cell type. Forty-two single atypical gland lesions (single gland adenomas) were detected in the upper part of the mucosa by serial sectioning. These single gland adenomas consisted of atypical epithelium with a narrow lumen and showed endophytic growth to the lamina propria mucosae. Complete serial sections also revealed that single gland adenomas had no direct continuity of the surrounding crypts of Lieberkühn. Single gland adenomas developed into microscopic adenomas consisting of several atypical glands by branching of the small atypical glands.