Inclusion Criteria:

          -  Histologically confirmed invasive lobular breast cancer, that is hormone
             receptor-positive and HER2-negative, measuring at least 1 centimeter (cm)
             radiographically or clinically, clinical stages I-III. Invasive lobular histology will
             be diagnosed at the enrolling institution for purposes of study participation.
             Subsequently, invasive lobular histology will be confirmed by central pathology
             review, but this central review will not be required prior to patient enrollment.

          -  Prior to initiation of study agents, study participants will be highly encouraged to
             undergo a baseline research core biopsy of their breast tumor. If this is not possible
             or the patient refuses, the pre-treatment tumor sample must be obtained from their
             archival diagnostic core biopsy. If definitive surgery is not performed at day 21-27
             after study treatment, a second post-treatment research core biopsy will need to be
             obtained from their breast tumor. For patients undergoing surgery, the second biopsy
             will be removed from the breast tumor tissue excised during their operation. Note: In
             the event that the baseline breast tumor biopsy performed for research purposes does
             not yield adequate tumor tissue for analysis of the primary and secondary endpoints,
             tissue will be requested from the patient's archival clinical diagnostic core biopsy
             if it is available.The patient will still remain on study and complete protocol
             therapy as planned in this unlikely event.

          -  Hormone receptor (HR) status of the invasive component must be documented before trial
             enrollment. The tumor must be HR-positive. HR will be considered positive if staining
             is 1% or greater for ER and/or PR. This will be determined at the enrolling
             institution for purposes of study participation and enrollment onto the trial.
             Subsequently, HR status will be confirmed by central pathology review, but this
             central review will not be required prior to enrolling the patient. HER2 status will
             be determined locally only, based upon current ASCO/CAP guidelines.

          -  Patients must be female.

          -  Participants must be fully postmenopausal.

          -  ECOG performance status of 0, 1 or 2.

          -  Adequate organ and marrow function as defined by a history and physical exam that
             rules out comorbidities that would be exclusions to participation in the study (see
             exclusion criteria) and clinical laboratory parameters as deemed clinically
             appropriate by the treating physician.

          -  Prior use of hormone contraceptives and replacement therapy is allowed (e.g., estrogen
             and/or progestin), but must have been discontinued at least 30 days prior to the study
             enrollment. Vaginal preparations (e.g., Vagifem® or Estring®)

          -  Participant must be aware of the nature of her malignancy, understand the study
             requirements and risks and be able and willing to sign a written informed consent
             document.

        Exclusion Criteria:

          -  Prior or concurrent use of hormonal therapy, chemotherapy, radiation therapy, or novel
             therapy to treat the current breast cancer, including any history of prior irradiation
             to the ipsilateral breast. Additionally, the patient must not have had hormonal
             therapy for breast cancer treatment or for breast cancer prevention within 2 years
             prior to study enrollment. (Note: Synchronous breast, cancer (including bilateral
             breast cancer) at separate sites is permissible, provided the patient does not receive
             medical treatments for breast cancer or radiation therapy to the ipsilateral breast
             during the 21 day study intervention period.

          -  Concurrent use of any other investigational agents.

          -  History of allergic reactions/hypersensitivity attributed to compounds of similar
             chemical or biologic composition to tamoxifen, anastrozole, or fulvestrant or any of
             their ingredients.

          -  History of thromboembolic disease or uterine cancer that is considered a
             contraindication to tamoxifen.

          -  Active hepatitis viral infections or a known history of liver disease, especially
             moderate (Child-Pugh Class B) to severe (Child-Pugh Class C) hepatic impairment.

          -  Uncontrolled current illness including, but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that would limit compliance with
             study requirements.

          -  HER-2 positivity.

          -  Increased Risk of bleeding: including a history of a bleeding diathesis and/or known
             history of severe thrombocytopenia. NOTE: Anticoagulant use is not a contraindication
             to fulvestrant, but caution is advised in administration in patients on
             anticoagulation. Patients on anticoagulation who will receive fulvestrant will have PT
             and aPTT/INR assessed at baseline.