Sections from 130 DMH-induced carcinomas in rats were reviewed. In 78% (74 out of 95) of the gland-forming adenocarcinomas, neoplastic glands displayed at the growing edge either a thinner layer or a partial loss of tumor cells ("pore" formation). The thinner epithelium appears to be a stage preceding the focal "destruction" of the tumor cells ("pore" formation). Through those glandular "pores" mucins, inflammatory cells or necrotic elements were being released free into the surrounding host tissues. It is theorized that those non-neoplastic "pseudopodial" forerunners (rich in proteolytic enzymes) encourage the degradation of the surrounding host tissues. The malignant cells surrounding glandular "pores" eventually grow around the secreted products to restore the continuity of the gland. The remodelling of the glands will guarantee a stepwise but everlasting tumor progression deeper into the host.