Neoplastic invasion in experimental carcinoma of the colon: abnormal differentiation and release of mucus.

Carcinomas of the colon were induced in F344 rats with dimethylhydrazine (20 mg/kg for 12 weeks). The invasive edges of the lesions were examined with the electron microscope. As in human colorectal cancer, the invasive edges show neoplastic cells with abnormal differentiation of apical cytoplasmic rootlets and processes at the basal or invasive edge of the cell, 'apical reversal'. Mucous carcinoma cells release material into the interstitial connective tissue matrix. The features may contribute to the complex phenomenon of neoplastic invasion.