Genistein in Preventing Breast Cancer in Women at High Risk for Breast Cancer

Inclusion Criteria: * No known soy intolerance * 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 * 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 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 * 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 * Female patient Exclusion Criteria: Women previously diagnosed with breast cancer will not be eligible unless all systemic therapy (including endocrine therapy) was completed at least one year previously * Currently pregnant, or planning to become pregnant during the study period * History of venous thrombosis within past year * Medical conditions, which, in the opinion of the investigators would jeopardize either the patient or the integrity of the data obtained * History of other cancer within the past five years, excluding non-melanomatous skin cancer, and non-invasive cervical cancer * Known soy intolerance * Unrecognized or uncontrolled thyroid disease, subjects may be on synthroid, but thyroid function must be in normal range or the patient's physician must document that the patient's thyroid is controlled. * Currently receiving any other investigational agents * Currently on coumadin, or other blood thinners * History of breast augmentation implants. * Rusults from patients who have \<4000 epithelial cells in either the first or the second random Fine-needle aspiration (rFNA) will not be included in the study.