Epidemiological studies reveal that the regular consumption of soybean reduces or suppresses breast cancer, being this fact associated to the presence of isoflavone, phytoestrogens in soybeans. It is believed estrogen that enables the growth of human mammary cancer and, consequently, the use of phytoestrogen has been considered to be an alternative therapy to the use of estrogen. In this study, the action of the isoflavones, a phytoestrogen that can be found in soybean, was evaluated in the growth of the Ehrlich tumor. This evaluation was based on the determination of weight, area and cellular proliferation. For that, an isoflavone suspension was given, via ip, in a dose of 20 mg/kg of weight, for 20 days. It was observed that the treatment can interfere with the cellular division cycle, based on the fact that the treatment with the isoflavone suspension reduced the number of mitosis found in the tumor tissue. However, no significant differences in weight and dimensions of tumor mass between the treated group and the control group were found, and that the necrosis area extension might be influencing these parameters, fact that deserves future investigation.

KEY WORDS: Ehrlich tumor; isoflavones; phytoestrogens