Inclusion Criteria:

- Women undergoing core needle biopsy for a breast abnormality suspicious for breast
cancer. Women who have undergone a core needle biopsy demonstrating breast cancer who
have not yet had any further therapy are also eligible so long as their core needle
biopsy is available for analysis.

- No prior therapy for breast cancer.

- Age 18 years or older.

- Ability to understand and the willingness to sign a written informed consent
document.

- Signed informed consent

Exclusion Criteria:

- History of parathyroid disease, hypercalcemia, or kidney stones.

- Supplemental vitamin D other than from a standard multiple vitamin or from standard
formulations of calcium and vitamin D (e.g. calcium citrate with vitamin D) within
the prior 6 months.

- History of renal failure requiring dialysis or kidney transplantation.

- Women who are known to be pregnant or who are nursing. (As vitamin D does not have
toxicity to the fetus, a negative pregnancy test is not a requirement to participate
in the study.)

- Supplemental calcium greater than 600 mg calcium per day during study.

- Patients for who initial treatment of their breast cancer will not be with breast
conserving surgery or mastectomy.

- Patients with locally advanced breast cancer

- Patients planned for neoadjuvant chemotherapy, hormonal therapy, or other systemic
therapy.

- Patients planned for preoperative radiation therapy.

- Patients with planned surgical therapy of their breast cancer that would not allow
for at least 10 days of vitamin D intervention.

- Any condition potentially interfering with subjects ability to comply with taking
study medication.

- Any medical condition that would potentially interfere with vitamin D absorption,
such as celiac sprue, ulcerative colitis.

- Current participation in another research study that would increase risk to subject,
in the opinion of the investigators