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