RATIONALE: Estrogen can cause the growth of tumor cells. Hormone therapy using therapeutic estradiol may fight breast cancer by lowering the amount of estrogen the body makes. Though estradiol initially produces stimulation of ER+ cancer cells, both laboratory and some clinical experience indicate that it may have the opposite effect on such cells, once they have become resistant to estrogen deprivation. In laboratory models, there is death of the "resistant" population after estradiol treatment, followed by restoration of sensitivity of the remaining cells to estrogen deprivation, as with an aromatase inhibitor. Exemestane may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Giving therapeutic estradiol together with exemestane may kill more tumor cells.