After a person is diagnosed with breast cancer, a doctor will want to determine whether or not the cancer has spread beyond the breast. The first place that gets checked is the network of lymph nodes (i.e., the axillary lymph nodes) under the arm.
In the past, a patient usually had to undergo an axillary lymph node dissection, whereby the lymph nodes are removed from under the armpit. Unfortunately, this procedure sometimes promotes chronic swelling or lymphedema in the arm. About to 10% to 20% of patients who undergo axillary lymph node dissection develop lymphedema.
Sentinel lymph node biopsy is a newer technique that can be used to make the same determination; i.e.: to assess whether or not the breast cancer has spread to an axillary lymph node. During a sentinel lymph node biopsy, either blue dye or a small amount of a radioactive substance (a radioisotope) is injected into the tumor. The first lymph node in which the dye or radioisotope collects is called the sentinel node. As the sentinel lymph node is the first area in the armpit region to which the breast cancer cells can spread, the sentinel lymph node is surgically removed and biopsied (examined under the microscope) to determine whether cancer cells are present.
If the sentinel lymph node does not contain any cancer cells, this result often eliminates the need to remove additional nodes in the axillary (armpit) area for evaluation.
Therefore, unlike axillary lymph node dissection, sentinel lymph node biopsy requires that only 1 to 3 of the lymph nodes under the arm be removed for evaluation.