Zearalenone is an estrogenic compound synthesized by Fusarium molds , a toxin with contaminant in food as a result of infection of grain. Zearalenone can enter the human food chain directly via ingestion of contaminated grain. Estrogens play important roles in the maintenance and function of the reproductive tract and mammary glands. The effects of neonatals exposure to zearalenone, estrogenic compound that stimulates growth of MCF-7 human breast cancer cell, were examined in females mice mammary glands tissue. In this study 20 females were examined. Female mice were divided into two groups. Control group received sesame oil and treatment group received Zearalenone (0.5, 1.0, or 2.0 mg/kg/days) per1 to 5 days after birth subcutaneously. All animals were perfused with paraformaldehyde in 70 days , and mammary glands were removed and post-fixed in paraformaldehyde. Crosssections of mammary glands were stained with hematoxyline and eosine and were evaluated histologically. In this study, we found no change in body weight of animals that received zearalenone comparable to control group. Also some ducts were irregularly thickened, and some end buds were expanded, which could suggest abnormal proliferation of the mammary gland. In study strongly support the role of zearalenone as a disruptor of mammary gland development when the toxin is given during critical periods such as neonatal life. Mammary glands are also sensitive to estrogenic chemicals, and timing and dosage of exposure of immature animals to xenoestrogens influence the development of mammary tumors. It is suggested that exposure of prepubertal mice to zearalenone causes an increase in mammary gland tumorigenic potential ,when the inside body estrogen level is low.

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