OUTLINE: This is a randomized, double-blind, multicenter study followed by an open-label study for both arms. Patients are stratified according to cytologic status (hyperplasia with atypia vs hyperplasia without atypia), mutation status (known carrier for BRCA1 or BRCA2 genes vs known not to be a carrier of mutant genes), menopausal status (premenopausal vs postmenopausal), estrogen-receptor status, and participating center. Patients are randomized to one of two treatment arms.