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 armpit (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 . 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
Currently, the most common way to check the lymph nodes for cancer is a sentinel node biopsy. With this procedure, the surgeon injects a radioactive substance (called a tracer) and/or a blue dye into the breast near the tumor. The surgeon then locates the sentinel node(s) by looking for the node(s) that has absorbed the blue dye or using a special device, the tracer. The surgeon usually removes one to three sentinel nodes. In certain cases, the surgeon may also remove one or two additional non-sentinel nodes. The pathologist checks the node(s) for cancer cells.
Sentinel node biopsy is a good way 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 positive rate) was low (about seven percent) .
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) .
Not everyone is a candidate for sentinel node biopsy (for example, a person who has had a prior lymph node surgery). And, sometimes, the sentinel node cannot be found. Sentinel node biopsy also may not be done if your physician feels suspicious lymph nodes and a needle biopsy shows the nodes contain cancer. In these cases, the surgeon will perform an axillary dissection.
When a sentinel node biopsy cannot be done (or if the sentinel node cannot be found), lymph nodes are assessed using an axillary dissection. During this procedure, a surgeon removes lymph nodes from different layers of tissue in the armpit. Ideally, at least 10 lymph nodes are removed. These nodes are then sent to a pathologist who views the nodes under a microscope to see how many of them contain cancer.
Advantages of sentinel node biopsy over axillary dissection
Sentinel node biopsy has some advantages over axillary dissection including:
- Less invasive with faster recovery time
- Fewer side effects (such as infection, lymphedema or nerve damage)