Abstract
Tumor cell proliferation and tumor vascularization were investigated in differentiated and undifferentiated colon carcinomas of the rat. The following results were found: 1, in both tumor types, vascularization is developed equally well; 2, both in the differentiated and in the undifferentiated carcinomas, the number of proliferating tumor cells decreases with increasing distance from the capillaries; at a distance of about 80 μm, there is no longer any noteworthy tumor cell proliferation; 3, the differentiated and undifferentiated carcinomas differ both in the level of the mitosis index and3H-thymidine labeling index as well as in their local proliferation pattern despite equal vascularization; 4, these differences must be based on factors which are independent of vascularization; they are attributed to proliferation properties which are inherent in the differently differentiated tumor cell populations. It is concluded from this that the actual proliferation behavior of a carcinoma is primarily dependent on the proliferation properties of the tumor cell population.