What are lymph nodes?
Lymph nodes are small clumps of immune cells that act as filters for the lymphatic system. The lymphatic system runs throughout the body (like the circulatory (blood) system) and carries fluid and cells.
The lymph nodes in the underarm (the axillary lymph nodes) are the first place breast cancer is likely to spread.
Figure 4.4 shows the location of the axillary lymph nodes.
What is lymph node status?
Lymph node status is highly related to prognosis.
- Lymph node-negative means the lymph nodes do not contain cancer.
- Lymph node-positive means the lymph nodes contain cancer.
Cancer found only in the breast (lymph node-negative) has the best prognosis. Prognosis is poorer when cancer has spread to the lymph nodes (lymph node-positive). The more lymph nodes that contain cancer, the poorer prognosis tends to be .
Assessing axillary lymph nodes
Physical exams and pathology exams
About 40 percent of women diagnosed with breast cancer have cancer in their axillary lymph nodes . These lymph nodes can sometimes be felt during a physical exam, but this does not take the place of a pathologist’s exam of the lymph nodes removed during a biopsy.
During a physical exam, a health care provider feels under the arm to check if the lymph nodes are enlarged. If they are, it is likely the cancer has spread. However, if the provider does not feel enlarged lymph nodes, this does not mean the nodes are negative (cancer-free).
The pathologist checks the nodes under a microscope. Nearly one-third of women with negative lymph nodes based on a physical exam have nodes with cancer found during the pathology exam . And, some women with enlarged nodes during a physical exam have cancer-free nodes . Thus, a pathologist's exam is needed to determine lymph node status.
Sentinel node biopsy and axillary dissection
Sentinel node biopsy is the most common way to check the axillary lymph nodes for cancer. Research has shown it is a good method to assess lymph node status [8-15]. A meta-analysis that combined the results of 69 studies showed sentinel node biopsy correctly predicted lymph node status in 96 percent of women with breast cancer . And, the chance of missing a positive lymph node (false negative rate) was low (about seven percent) .
With a sentinel node biopsy, the surgeon injects a radioactive substance (called a tracer) and/or a blue dye into the breast near the tumor. The first node(s) to absorb the tracer or dye is called the sentinel node(s). (The sentinel node(s) is the first place breast cancer is likely to spread.) The surgeon locates the sentinel node(s) by looking for the node that has absorbed the tracer (using a special device called a gamma probe) or the dye (which turns the lymph node(s) blue). The tracer or blue dye identifies one to several (usually fewer than five) nodes as the sentinel nodes. The surgeon removes the sentinel node(s). A pathologist checks the node(s) for cancer cells.
If cancer is not found in the sentinel node (the sentinel node is negative), it is unlikely that other axillary lymph nodes have cancer.
If the sentinel node does contain cancer cells (the sentinel node is positive), more nodes are sometimes removed with a procedure called axillary dissection (see more below). The goal of axillary dissection is to check how many lymph nodes have cancer. This may help determine if a person will have chemotherapy after surgery. It also reduces the chances of cancer returning in the axillary lymph nodes. Some people with a positive sentinel node may not need axillary dissection.
Axillary dissection removes more tissue than a sentinel node biopsy. Because it disrupts more of the normal tissue in the underarm area, axillary dissection is more likely to affect arm function and cause lymphedema. For this reason, sentinel node biopsy is the preferred first step to check lymph nodes.
Learn more about lymphedema.
Who cannot have a sentinel node biopsy?
In some cases, an axillary dissection instead of a sentinel node biopsy is advised. This usually occurs when:
- A person cannot have a sentinel node biopsy (for example, a person who has had a prior lymph node surgery)
- The sentinel node cannot be found
- The physician feels suspicious lymph nodes and a needle biopsy prior to surgery shows the nodes contain cancer
Topics under study
The accuracy of sentinel node biopsy is still under study in people who have locally advanced breast cancer.
Although still under study, early findings suggest sentinel node biopsy may be a good way to assess lymph node status for those who get chemotherapy before surgery (neoadjuvant chemotherapy) .