When breast cancer spreads, it typically travels to the nearby lymph nodes under the armpit.

If you have been diagnosed with breast cancer, it’s important to find out how far the cancer has spread. This information is used to stage the cancer and to help drive the treatment plan. This is done by checking one or more of the lymph nodes under the arm (axillary lymph nodes) by removing them and examining them under a microscope.

When the lymph nodes contain cancer cells, this is an indication that cancer cells have also spread to other parts of the body. Treatment decisions will often depend on whether cancer is found in the lymph nodes.


Biopsy of an enlarged or abnormal lymph node

If any of the lymph nodes under the arm or around the collar bone are swollen, or abnormal appearing on breast ultrasound, they may be checked for cancer cells with a needle biopsy.

Types of lymph node surgery

Even if the nearby lymph nodes are not enlarged or abnormal appearing on imaging, they will still need to be checked for cancer to ensure that cancer has not spread outside of the breast.

Lymph node surgery is often done as part of the main surgery to remove the breast cancer, but in some cases it might be done as a separate operation.


Sentinel lymph node biopsy (SLNB)

In a sentinel lymph node biopsy (SLNB), the surgeon finds and removes the first lymph node(s) to which a tumor is likely to spread (called the sentinel nodes). To do this, the surgeon injects a radioactive substance and/or a blue dye into the tumor, the area around it, or the area around the nipple. The breast lymphatic vessels will carry these substances along the same path that the cancer would likely take. The first lymph node(s) the dye or radioactive substance travels to will be the sentinel node(s).

The idea behind the sentinel lymph node technique is that if any cancer cells have spread outside of the breast, they would be found within the first draining lymph node of the breast.

After the substance has been injected, the sentinel node(s) can be found by using a special device to detect radioactivity in the nodes, and by looking for nodes that have turned blue. The surgeon cuts the skin over the area and removes the node(s) containing the dye or radioactivity.

The few removed lymph nodes are then checked closely for cancer cells by a doctor called a pathologist. This is sometimes done during the surgery. This way, if cancer is found in the sentinel lymph node(s), the surgeon may go ahead with a full axillary dissection (ALND) to remove more lymph nodes while you are still on the operating table. If no cancer cells are seen in the node(s) at the time of the surgery, or if the sentinel node(s) are not checked by a pathologist at the time of the surgery, they will be examined more closely over the next several days.

If cancer is found in the sentinel node(s) later, the surgeon may recommend a full ALND at a later time to check more nodes for cancer. Recently, however, studies have shown that in some cases it may be just as safe to leave the rest of the lymph nodes behind. This is based on certain factors, such as the size of the breast tumor, what type of surgery is used to remove the tumor, and what treatment is planned after surgery. Based on the studies that have looked at this, skipping the ALND may be an option for women with tumors 5 cm (2 inches) or smaller who are having breast-conserving surgery followed by radiation. For some women who have had mastectomy and will also have radiation, skipping the ALND might be an option.

If there is no cancer in the sentinel node(s), it’s very unlikely that the cancer has spread to other lymph nodes, so no further lymph node surgery is needed.


Axillary lymph node dissection (ALND)

In this procedure, anywhere from about 10 to 40 (though usually less than 20) lymph nodes are removed from the area under the arm (axilla) and checked for cancer spread. ALND is usually done at the same time as a mastectomy or partial mastectomy, but it can be done in a second operation. This procedure is becoming less common as recent data has shown that it may be safe to remove fewer lymph nodes, but it may be necessary for some patients.


Side effects of lymph node surgery


One possible long-term effect of lymph node removal is swelling in the arm or chest called lymphedema. Because any excess fluid in the arms normally travels back into the bloodstream through the lymphatic system, removing the lymph nodes sometimes blocks this drainage from the arm, causing this fluid to build up.

The risk is thought to be in the range of 3-7% in women who have a SLNB and around 30% in women who have a ALND . It may be more common if radiation is given after surgery or in women who are obese. Sometimes the swelling lasts for only a few weeks and then goes away. But in some women, it lasts a long time. If your arm is swollen, tight, or painful after lymph node surgery, be sure to tell someone on your cancer care team right away.

Very commonly, our breast cancer surgeons will refer you to a lymphedema specialist after your operation, to evaluate for and use techniques to prevent lymphedema.


Limited arm and shoulder movement

You may also have limited movement in your arm and shoulder after surgery. This is more common after ALND than with SLNB. Your doctor may advise exercises and send you to a physical therapy specialist to help prevent you from having permanent problems.



Numbness of the skin on the upper, inner arm is a common side effect because the nerve that controls sensation here travels through the lymph node area.



American Cancer Society

Susan G Komen