Hormonal Effects on Tc-99m Sestamibi Uptake in the Breast

Arm 1 Inclusion Criteria: * age 35-45 * have regular menstrual cycles as defined by having menstrual cycle length of 25-31 days, with menstrual flow of 2-7 days, and no intermenstrual spotting or bleeding. * have had a negative screening mammogram within one year prior to the MBI studies that is available for comparison. Exclusion Criteria: * currently using any exogenous hormones (e.g., hormonal contraceptives, sex steroid hormones) or any estrogen receptor modulating drugs (e.g., tamoxifen, raloxifene) or any aromatase inhibitors * have a personal history of any cancer, except non-melanomatous skin cancer * unable to understand and sign the consent form * pregnant or lactating * physically unable to sit upright and still for 30 minutes Arm 2 Inclusion Criteria: * scheduled to begin one of the following regimens of HT: * Any dosage of any formulation of systemic estrogen therapy in the setting of a prior hysterectomy * Any dosage of continuous estrogen plus monthly, cyclic progesterone therapy where the progesterone therapy is the oral, micronized formulation * had a negative screening mammogram within one year prior to the MBI studies that is available for comparison. Exclusion Criteria: * have a personal history of any cancer, except non-melanomatous skin cancer * unable to understand and sign the consent form * pregnant or lactating * physically unable to sit upright and still for 30 minutes Arm 3 Inclusion Criteria: * scheduled to begin treatment with tamoxifen Or are currently being treated with tamoxifen (for \> 1 month) and have had an MBI scan performed prior to its initiation * have had or will have the following test performed at Mayo Clinic: #87966, Cytochrome P450 2D6 genotyping for Tamoxifen Hormonal Therapy * have had a screening or diagnostic mammogram within one year of the MBI studies that is available for comparison. Exclusion Criteria: * are using or have used any exogenous hormones (e.g., hormonal contraceptives, sex steroid hormones), any estrogen receptor modulating drugs other than tamoxifen, or any aromatase inhibitors from the time of 1 month prior to the first MBI until completion of the second MBI. * have been treated or will be undergoing treatment with systemic chemotherapy or external radiation beam therapy to the breast from the time of 6 months prior to the first MBI until the completion of the second MBI. * unable to understand and sign the consent form * pregnant or lactating * physically unable to sit upright and still for 30 minutes