Inclusion Criteria

DISEASE CHARACTERISTICS:

- At increased risk of developing breast cancer in ≥ 1 previously unaffected breast, as
defined by any of the following:

- Estimated 5-year risk of developing breast cancer using the Gail model, as
defined by 1 of the following:

- Gail score ≥ 1.66%

- Gail score ≥ 0.1% for women age 20-29 years

- Gail score ≥ 1.0% for women age 30-39 years

- Estimated 5-year risk of developing breast cancer using the Claus model

- Claus score ≥ 1.66%

- Claus score ≥ 0.1% for women age 20-29 years

- Claus score ≥ 1.0% for women age 30-39 years

- Prior diagnosis of unilateral in situ or invasive breast cancer OR history of
atypical hyperplasia

- BRCA 1 and/or BRCA 2 positivity

- History of lobular carcinoma in situ

- No evidence of breast cancer, as determined by a negative mammogram within the past 6
months and a history and physical

- No previously diagnosed breast cancer unless all systemic therapy (including
endocrine therapy) was completed at least 1 year ago

PATIENT CHARACTERISTICS:

- Female patient

- Pre- or postmenopausal

- ECOG performance status 0-1

- Hemoglobin > 10.0 g/dL

- Platelet count > 100,000/mm^3

- Absolute neutrophil count > 1,000/mm^3

- Creatinine < 2.0 mg/dL

- SGPT < 82 U/L

- SGOT < 68 U/L

- Bilirubin < 3 mg/dL* NOTE: * Patients with a higher level of bilirubin due to a
familial metabolism may be eligible at the discretion of the investigator

- Life expectancy > 2 years

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective barrier contraception

- Must be willing to keep a dietary diary

- No venous thrombosis within the past year

- No known soy intolerance

- No unrecognized or poorly controlled thyroid disease

- No other cancer within the past 5 years except nonmelanomatous skin cancer or
noninvasive cervical cancer

- No other medical condition that, in the opinion of the investigator, would jeopardize
either the patient or the integrity of the data obtained

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- None of the following for ≥ 2 weeks before the first random fine needle aspiration
and during study participation:

- Oral contraceptives

- Soy supplements

- High soy-containing foods

- Fish oil supplements

- Multivitamins

- Vitamins C and E

- Daily aspirin or nonsteroidal anti-inflammatory drugs

- No other concurrent investigational agents

- No concurrent warfarin or other blood thinners