Patient description: The patient is a 42 year-old postmenopausal woman who had a screening sonogram which revealed an abnormality in the right breast. She had no palpable masses on breast exam. Core biopsy was done and revealed a 1.8 cm infiltrating ductal breast carcinoma in the left upper outer quadrant. Lumpectomy was done and the surgical margins were clear. The tumor was HER2-positive and ER/PR negative. Axillary sampling revealed 1 positive lymph node out of 12 sampled. CXR was unremarkable. She is using “well women” multivitamins daily and no other medication. She smokes frequently and consumes alcohol occasionally. She is in a relation with only one partner and has a history of 3 pregnancies and live births. She breastfed all three children.

Clinical trial eligibility criteria: eligible ages (years): 0.0-999.0,  Breast Cancer Breast Neoplasms Women and men at increased risk for the development of breast cancer by at least one of the following Histologically documented ductal carcinoma in situ (DCIS), including DCIS with minimal invasion or microinvasion. Histologically documented lobular neoplasia, including lobular hyperplasia and lobular carcinoma in situ (LCIS). Histologically documented atypical ductal hyperplasia in postmenopausal women. Histologically documented atypical ductal hyperplasia in premenopausal women with 1 first-degree relative (mother or sister) diagnosed with breast cancer. Histologically documented atypical ductal hyperplasia in premenopausal women with 3 or more relatives diagnosed with breast cancer provided at least 1 is a second-degree relative. 3 or more first or second-degree relatives diagnosed with breast or ovarian cancer with at least 1 diagnosed with breast cancer. 2 or more premenopausal (under age 50) first-degree relatives diagnosed with breast cancer. 1 or more first-degree relatives diagnosed with breast cancer if at least 1 relative in the extended pedigree had ovarian cancer. 3 or more relatives with breast cancer with at least 1 first-degree relative diagnosed with premenopausal breast cancer. Previously diagnosed Stage I breast cancer with surgery and/or radiotherapy only (without prior adjuvant chemo or hormonal therapy). Positive for the BRCA1/BRCA2 gene. No history of other invasive breast cancer. No evidence of malignancy on breast and gynecologic exams. Participants with a family history of breast cancer will be seen in consultation by the Family Studies Branch, NCI. PRIOR/CONCURRENT Mastectomy or lumpectomy plus radiotherapy required prior to entry for patients with DCIS. Patients with DCIS who have participated in protocol NCI-MB-348 eligible. No participation in any other breast cancer prevention study involving pharmacologic intervention. No prior chemotherapy or hormonal therapy for invasive breast cancer. At least 3 months since estrogen or progesterone replacement therapy or hormonal contraceptives. Age: 35 and over. Performance status: Ambulatory. Life expectancy: At least 10 years. Hematopoietic: Complete blood count normal. Hepatic: Bilirubin normal. Alkaline phosphate normal. AST normal. PT, PTT normal. No history of bleeding disorder. No history of chronic hepatitis or cirrhosis. Renal:Creatinine less than 1.5 mg/dL. Cardiovascular: No history of deep venous thrombosis. No history of pulmonary embolus. Other: No allergy to any study medication. Capable of tolerating multiple diagnostic procedures. No history of abnormal vaginal bleeding. Hysterectomy for vaginal bleeding of benign etiology allowed. No history of retinal disease, macular degeneration, or night blindness. No medical or psychiatric risk due to nonmalignant systemic disease that would preclude study participation. No history of malignancy except: Curatively treated nonmelanomatous skin cancer. Curatively treated in situ cervical carcinoma. Hodgkin's disease treated more than 5 years ago. No pregnant women. Adequate contraception required of fertile patients during and for 12 months after fenretinide and for 2 months after tamoxifen