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.
Lymph node status is highly related to prognosis.
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 .
For a summary of research studies on lymph node status and breast cancer survival, visit the Breast Cancer Research Studies section.
Lymph node status is related to tumor size. The larger the tumor, the more likely it is that the breast cancer is lymph node-positive (the axillary lymph nodes contain cancer) .
Positive 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 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 [10-13].
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) .
In some cases, an axillary dissection (which removes more tissue than a sentinel node biopsy) is advised.
Learn more about sentinel node biopsy, axillary dissection and lymph node assessment.
For a summary of research studies on sentinel node biopsy and lymph node status, visit the Breast Cancer Research Studies section.
The accuracy of sentinel node biopsy is still under study in people who have locally advanced breast cancer.
Facts for Life: Axillary Lymph Nodes
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