Patient description: The patient is a 45-year-old postmenopausal woman with cytologically confirmed breast cancer. A core biopsy revealed a 3 cm invasive ductal breast carcinoma in the left upper outer quadrant. The tumor is HER2-positive and ER/PR negative. Axillary sampling revealed 5 positive lymph nodes. CXR was remarkable for metastatic lesions. The patient is using multivitamins and iron supplements. She does not smoke or consume alcohol. She is not sexually active and has no children. She is a candidate for tumor resection and agrees to do so prior to chemotherapy.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Breast Cancer Female waivers are not permitted. Subjects must meet all of the and  to be registered to the study. Study treatment may not begin until a subject is registered. 2. Patients must provide informed written consent 3. ECOG performance status 0-1. 4. Clinical stage operable I, II or III invasive mammary carcinoma, which is ER-positive by IHC and HER2-negative by Herceptest (0 or 1+) or not amplified by FISH as per routine clinical testing Patients who have measurable residual tumor at the primary site Patients who will undergo surgical treatment with either segmental resection or total mastectomy 5. Measurable tumor i. Measurable disease: a mass that can be reproducibly measured by physical exam and calipers or ultrasound and is at least 1 cm in size 6. The pathology report from the initial diagnosis has been reviewed by either UTSW or Parkland Hospital, Department of Pathology and meets criteria. Available core biopsies from the time of diagnosis have been requested. These may the paraffin block or sections from the paraffin-embedded tumor blocks. 7. Post-menopausal female subjects ≥18 years of age, as defined by any of the following Subjects at least 55 years of age Subjects under 55 years of age and amenorrhoeic for at least 12 months or follicle-stimulating hormone (FSH) values ≥40 IU/L and estradiol levels ≤40 pg/mL (140 pmol/L) or in postmenopausal ranges per local or institutional reference ranges Prior bilateral oophorectomy or prior radiation castration with amenorrhea for at least 6 months (There is no upper age limit for enrollment to this study) 8. No prior chemotherapy for this primary breast cancer. 9. Patients with a prior history of contralateral breast cancer are eligible if they have no evidence of recurrence of their initial primary breast cancer. 10. Women may have been taking tamoxifen or raloxifene as a preventive agent prior to study entry but must have discontinued the drug for at least 21 days prior to study enrollment. 11. Subjects must have ended hormone replacement therapy (HRT) (e.g., conjugated estrogens tablets, USP, [Premarin]), at least 7 days prior to receiving the first dose of randomized therapy. 12. Patients must have adequate hepatic and renal function. All tests must be obtained less than 4 weeks from study entry. This includes: 1. Creatinine <1.5X upper limits of normal 2. Bilirubin, SGOT, SGPT <1.5X upper limits of normal 13. Able to swallow and retain oral medication Patients with locally advanced disease who are candidates for other preoperative chemotherapy at the time of initial evaluation. This may patients with locally advanced disease such as Inflammatory breast cancer (T4d) Fixed axillary lymph node metastases (N2) Metastasis to ipsilateral internal mammary node (N3) 2. Locally recurrent breast cancer 3. Evidence of distant metastatic disease (i.e. lung, liver, bone, brain, etc.) 4. Serious medical illness that in the judgment of the treating physician places the patient at high risk of operative mortality. 5. Severe uncontrolled malabsorption condition or disease (i.e. grade II/III diarrhea, severe malnutrition, short gut syndrome) 6. Dementia, altered mental status, or any psychiatric condition that would prohibit the understanding or rendering of informed consent. 7. Use of an investigational drug within 30 days or 5 half-lives, whichever is longer, preceding the first dose of letrozole