Rectum is divided into three distinctive regions (pelvic peritoneal, pelvic subperitoneal and perineal) regarding the regions where it is crossing through. Those three parts are individually not only due to their relation but due to their blood supply, also. The differences occur among them when one of them is involved into a neoplastic process. Both types of pelvic rectal tumors behave quite in the same way but those involving perineal rectum are much different. This is because they purchase a smaller number of anastomosis; when a tumor monopolizes a wide vessel the possibility to grow and become a metastasis is much more likely. These two processes (growth and metastasis) are directly related to the size of its supplying artery. On the other hand, a pelvic rectal tumor is more likely to metastasis by blood flow then a perineal rectal one. The last one will rather send clone cells by lymphatic drainage or will disseminate into the soft tissues around it. In this study, we want to propose an anatomical mathematical model for each of the rectal tumors, depending on their stages also. We used specimens from 24 patients and analyzed them using arteriography; we connected the results of mathematical counting of micro vessels density in a specific area with already known medical aspects regarding their diagnosis, treatment and evolution. The goal of the study concerns the prognosis of the patients (with or without surgical treatment) and the example is useful in rectal tumors staging.