Study the Use of Magseed and Sentimag to Localize Axillary Lymph Nodes

Study Visits:

If participant agrees to take part in this study, participant will have 3 study visits:

Marker Placement Procedure:

If participant can become pregnant, blood (about 1 teaspoon) or urine will be collected for a
pregnancy test before participant's marker placement procedure. To take part in this study,
participant must not be pregnant.

After numbing the skin with a local anesthetic, the Magseed marker will be injected into or
near in or near the lymph node under participant's arm. The person injecting the Magseed
marker may use an ultrasound or mammogram to position the needle properly. Participant will
leave with a dressing under participant's arm.

Targeted Lymph Node Removal:

After participant has been given general anesthetic to make participant sleep, participant's
doctor will perform the lymph node removal procedure. As part of the procedure, the doctor
will use a handheld device to scan under participant's arm and locate the marker. Participant
will sign a separate consent form that explains the surgical procedure and its risks.

Following removal of the lymph node(s) and the marker, the study testing is completed and
participant's doctor will continue with participant's standard care in the operating room.

Post-Operative Visit:

Within 6-22 days after participant's surgery, participant will return for a routine follow-up
visit. During visit, participant will be asked questions about any side effects or injuries
since participant's surgery and about any drugs participant may be taking. It should take
about 10 minutes to answer these questions.

Length of Study Participation:

Participation in this study will be over when participant completes the visit after surgery.
Participant's total time in the study will be about 3-6 weeks.

Inclusion Criteria:

1. Age 18 years or more at the time of consent

2. Histologically confirmed cT0-4, N1 breast cancer

3. Axillary lymph node metastasis with pathologic confirmation by needle biopsy

4. Clip placed in the sampled axillary lymph node at the time of the biopsy

5. Received neoadjuvant chemotherapy prior to surgical resection

6. Scheduled for targeted axillary dissection (defined as selective localization and
removal of the clipped node and SLND)

7. ECOG performance status 0-2

Exclusion Criteria:

1. Distant metastases

2. Inflammatory breast cancer

3. Prior surgical axillary procedure including SLND or axillary node excision

4. Prior history of breast cancer in the ipsilateral breast

5. History of lymphoma

6. The subject is pregnant

7. Previous radiation to the breast or axilla

8. Pacemaker of other implantable device in the chest wall