Letrozole in Treating Postmenopausal Women With Stage I, II or III Breast Cancer That Can Be Removed by Surgery

DISEASE CHARACTERISTICS: * Diagnosis of invasive breast cancer * Clinical stage I, II, or III disease * Resectable disease * Measurable disease, defined as a mass that can be reproducibly measured by physical examination and/or ultrasound and is at least 1 cm in size by ultrasound * Patients with measurable residual tumor at the primary site allowed * Estrogen receptor-positive tumor by immunohistochemistry (IHC) * HER2-negative tumor by Herceptest (0 or +1) OR HER2 not overexpressed by fluorescence in situ hybridization (FISH) * Planning to undergo surgical treatment with either segmental resection or total mastectomy with or without lymph node evaluation * Must have core biopsies from the time of diagnosis available (may include sections of paraffin-embedded material) * Prior contralateral breast cancer allowed provided there is no evidence of recurrence of the initial primary breast cancer * Patients with locally advanced disease who are candidates for preoperative chemotherapy at the time of initial evaluation are not eligible * Locally advanced disease is defined by any of the following: * Primary tumor ≥ 5 cm (T3) * Tumor of any size with direct extension to the chest wall or skin (T4a-c) * Inflammatory breast cancer (T4d) * Fixed axillary lymph node metastases (N2) * Metastasis to ipsilateral internal mammary node (N3) * No locally recurrent disease * No evidence of distant metastatic disease (i.e., lung, liver, bone, or brain metastases) PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Postmenopausal, as defined by any of the following: * 55 years of age and over * Under 55 years of age and meets 1 of the following criteria: * Amenorrheic for at least 12 months * Follicle-stimulating hormone (FSH) ≥ 40 IU/L and estradiol levels ≤ 20 IU/L * Has undergone prior bilateral oophorectomy or radiation castration AND has been amenorrheic for at least 6 months * Bilirubin ≤ 1.5 times upper limit of normal (ULN) * SGOT and SGPT ≤ 1.5 times ULN * Creatinine ≤ 1.5 t times ULN * Able to swallow and retain oral medication * No serious medical illness that, in the judgment of the treating physician, places the patient at high risk for operative mortality * No malabsorption syndrome, ulcerative colitis, or other disease significantly affecting gastrointestinal function * No other malignancy within the past 5 years except for completely resected nonmelanoma skin cancer or successfully treated in situ carcinoma * No dementia, altered mental status, or any psychiatric condition that would preclude the understanding or rendering of informed consent * No severe uncontrolled malabsorption condition or disease (i.e., grade II/III diarrhea, severe malnutrition, or short gut syndrome) PRIOR CONCURRENT THERAPY: * See Disease Characteristics * At least 21 days since prior tamoxifen or raloxifene as a preventive agent * At least 7 days since prior hormone replacement therapy (e.g., conjugated estrogens \[Premarin\]) * No prior resection of the stomach or small bowel * More than 30 days or 5 half-lives, whichever is longer, since prior investigational drugs * No prior chemotherapy for this primary breast cancer * No other concurrent investigational agents * No other concurrent anticancer therapy (e.g., chemotherapy, radiotherapy, immunotherapy, hormonal therapy, or any other biologic therapy)