Mammary tumors are common in feline medicine. They are often malignant with a high risk of metastasis and guarded prognosis. Intact females are at greater risk of its development than spayed ones. The underlying cause is unknown, however there are a few predisposing factors. A strong relationship was established between progestagens and mammary tumors’ occurrence. It was also proven that gonadectomy prior to first estrus significantly lowers their incidence. Since, intact females are those to receive exogenous progestagens, it is difficult to confirm the difference between drug derived and internally synthesized progestagens and the subsequent pathological changes. In the reported case, queen received medroxy- progesterone acetate for 10 years, despite it was ovariectomized when one year old. The role of endogenous reproductive hormones in the etiology of the mammary neoplasia and CEH is excluded, the mastopathic and metropathic changes, can only be attributed to the effect of exogenous progestagene administration.

Key words: Adenocarcinoma, Cat, Medroxyprogesterone acetate