RATIONALE: Drugs used in chemotherapy work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving chemotherapy before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed.

PURPOSE: This phase II trial is studying surgery to remove the sentinel lymph node and axillary lymph nodes after chemotherapy in treating women with stage II, stage IIIA, or stage IIIB breast cancer.

This is a multicenter study. Patients who plan to receive or have received neoadjuvant chemotherapy are eligible. Patients undergo examination for breast and axilla lymph adenopathy and then undergo ultrasound of the axillary nodes prior to registration to confirm eligibility and after completion of neoadjuvant chemotherapy. Within 12 weeks of completing neoadjuvant chemotherapy, patients undergo a mastectomy or lumpectomy (per surgeon discretion) including both sentinel lymph node surgery and axillary lymph node dissection. The primary and secondary objectives of the study are described below.

Primary Objective:

1. To determine the false negative rate for sentinel lymph node (SLN) surgery. Among the patients who have at least one sentinel lymph node identified and removed, false negative rate is defined as the number of patients declared to have no evidence of cancer in the SLN and are found to have at least one positive lymph node in the ALND divided by the total number of patients with at least one positive axillary lymph node by ALND.

Secondary Objectives:

1. To determine how the axillary ultrasound status of the patient upon completion of preoperative chemotherapy (evidence of residual lymphadenopathy on the ultrasound examination versus no evidence of lymphadenopathy in the ultrasound examination) affects the false negative rate of SLN and how sonographic findings correlate with residual disease on final pathology.
2. To determine the node status of patients after preoperative chemotherapy. Patients will be classified as node positive if they were determined to have at least one positive lymph node by SLN or ALND. Patients will be classified as node negative if all nodes examined by SLN and ALND were negative.
3. To determine whether the false-negative rate for SLN surgery after preoperative chemotherapy is related to the extent of residual cancer burden (RCB) overall, or separately in the breast or regional nodal basin.
4. To evaluate pathological complete response (pCR) rates (defined as no invasive disease in breast or lymph nodes) and disease-free survival (DFS) rates in node-positive patients receiving preoperative chemotherapy.

After completion of surgery, patients will visit the office for follow-up exams at 1-2 weeks then patients are followed every 6 months for 2 years, yearly for 2 years, then every other year for 6 years. The study closed to accrual and treatment on 5/29/12.

Eligibility Criteria:

1. ≥ 18 years old
2. ECOG/Zubrod Performance Status 0-1
3. Female. Note: Men are excluded from this study because the number of men with breast cancer is insufficient to provide a statistical basis for assessment of effects in this subpopulation of people with breast cancer.
4. Histologic diagnosis of invasive breast cancer, clinical stage T0-4 N1-2 M0 (excluding inflammatory breast cancer).
5. FNA biopsy or core needle biopsy of an axillary node documenting nodal disease at time of diagnosis and prior to preoperative chemotherapy.
6. Preoperative chemotherapy must be completed or planned for patient. NOTE: Patients enrolling on studies involving preoperative chemotherapy (through cooperative groups or institutional studies) may be eligible for this study, provided sentinel node surgery prior to preoperative chemotherapy was not required in the other studies.
7. No prior ipsilateral axillary surgery, such as excisional biopsy of lymph node(s) or treatment of hidradenitis.
8. No prior SLN surgery/excisional lymph node biopsy for pathological confirmation of axillary status.