Prevention Strategy for Pre-Menopausal Women at High Risk for Development of Breast Cancer

PARTICIPANT SELECTION * Risk Level Required for RPFNA Screening for Eligibility * Given the low probability of side effects and the desire to be able to generalize results to a moderate as well as high risk population, the target cohort is pre-menopausal women who have a relative risk for breast cancer which is 2-fold or greater than that of the average woman in their age group by virtue of any one of the following conditions: * A 1st or 2nd degree relative with breast cancer diagnosed under the age of 60 * A prior biopsy indicating proliferative breast disease, atypical hyperplasia, or LCIS * Multiple prior breast biopsies regardless of histology * 50% or higher estimated mammographic density on visual inspection * Prior or current RPFNA evidence of atypia * Known carrier of a BRCA1 or 2 mutation. * Age, Life-Style and Medical Eligibility Criteria for Tissue Screening Candidates for tissue screening for this study are pre-menopausal women who meet the risk criteria above and all of the following demographic and medical criteria: * Age 21 to 49 (limiting the maximum age to 49 will reduce the possibility of reduction in Ki-67 due to entry into menopause transition during the study). * Stable hormonal status for the previous 6 months (has not stopped or started oral contraceptives, or experienced lactation or pregnancy) and willing to maintain same status while on study. * BMI \< 40 kg/m2. * Has had at least 4 menstrual cycles in past year * If regularly undergoing screening mammography, must have been performed within 9 months prior to baseline RPFNA, and interpreted as not suspicious for breast cancer * Breast exam interpreted as normal (not suspicious for cancer). * Exclusion Criteria for Screening RPFNA and Study Participation Candidates are ineligible for tissue screening if they meet any of the following conditions: * Consumption of systemic antibiotics during the 3 weeks prior to baseline RPFNA. Systemic antibiotics reduce intestinal bacteria and thus the ability to convert SECO to ENL. * Consumption of supplements containing SDG (flaxseed or sesame seed) during the 3 weeks prior to baseline RPFNA. ( Consumption of foods containing flaxseed or sesame seed are OK.) * Use of any selective estrogen receptor modulator or aromatase inhibitor (tamoxifen, raloxifene, arzoxifene, acolbifene, anastrozole, exemestane, letrozole) within the previous 6 months. * Currently enrolled on an interventional investigational study. * Bilateral breast implants. * Invasive breast cancer or other invasive cancer diagnosis within five years. * Metastatic malignancy of any kind.excluding Hodgkin's or non-Hodgkin's lymphoma. * Current anticoagulant use. * Consumption of coumadin, fish oil, or other anticoagulants during the 3 weeks prior to baseline RPFNA. * Any other condition or intercurrent illness that in the opinion of the investigator makes the subject a poor candidate for RPFNA or the trial. * Inclusion Criteria for Study Entry * RPFNA performed in the follicular portion (day 1-10) of the menstrual cycle. Note that day 1 is defined as the first day of bleeding. * RPFNA specimen exhibits hyperplasia +/- atypia (Masood score of ≥13) with ≥500 cells on the cytology slide. * Ki-67 ≥2% positivity (≥500 cells). * Willing to continue without oral contraceptives throughout the duration of the study participation (12 months). Non-oral contraceptives are permissible. If heterosexually active, must be agreeable to use some non-hormonal form of contraception during the trial or husband or partner must have had a vasectomy. (Safety of SDG during pregnancy has not been documented). * Have reasonable organ function as documented by metabolic chemistry profile. * Willing to undergo a history and physical at baseline and 12 months and be contacted periodically by the trial coordinator during the 12 month study period. * Willing to have blood drawn at baseline and twelve months. * Able to understand and willing to provide informed consent for the RPFNA's and study participation.