The data that would be generated is no longer clinically novel.

This research protocol is studying the accuracy of the sentinel lymph node biopsy procedure in breast cancer patients who have cancer cells in the lymph nodes in the armpit (axilla) who have received chemotherapy or endocrine therapy prior to having surgery (neoadjuvant therapy).

• This research study is a Pilot Study, which is the first time investigators are examining this study intervention locally; although this intervention has been studied nationally in published clinical trials.
• In this research study, the investigators are studying the accuracy of the sentinel lymph node biopsy procedure in breast cancer patients who have cancer cells in the lymph nodes in the armpit (axilla) who have received chemotherapy or endocrine therapy prior to having surgery (neoadjuvant therapy).
• A sentinel lymph node biopsy is a surgical evaluation of the lymph nodes in the underarm area in patients who have early breast cancer. Approximately, two-five nodes are removed from the underarm area for evaluation. The sentinel lymph node biopsy is performed in patients with breast cancer to determine if there are cancer cells in the lymph nodes in the armpit.
• The sentinel lymph node biopsy procedure is performed by injecting one or two dyes into the breast, which then travel to the armpit region via small vessels in the immune system. These nodes are called the sentinel lymph nodes. They represent the first nodes that drain the breast tissue. They are closely evaluated by a Pathologist to determine if cancer cells are present.
• This information allows physicians to know how far the cancer may have spread and recommend therapies accordingly.
• If sentinel lymph node biopsy is determined to be accurate in patients who are known to already have cancer cells in the axillary lymph nodes who receive neoadjuvant therapy, then in the future, many of the patients in this population may be spared the procedure of a full axillary lymph node dissection, which removes a larger number of lymph nodes and thus has increased risks and side-effects.

Inclusion Criteria:

• Eligible patients will include any patients with biopsy-proven breast cancer and biopsy-proven axillary lymph node metastases at Beth Israel Deaconess Medical Center who are candidates for Neoadjuvant Chemotherapy or Neoadjuvant Endocrine therapy.
• A core needle biopsy or fine needle aspiration is acceptable for diagnosis of metastatic disease in lymph nodes.
• Patients will be identified as possible participants in the Radiology Imaging suites and Breast Surgery Clinics.

Exclusion Criteria:

-Patients with inflammatory breast cancer or distant metastases will be excluded from participating in this study