The lymphatic system drains lymph from the breast to the lymph nodes in the armpit or axilla. In order to determine the potential for spread of breast cancer, it is essential to examine these nodes for cancer cells.

When cancer cells separate from the primary (original) tumor and circulate through the lymph or blood to other places in the body, another (secondary) tumor can form. This process is called metastasis.

The sentinel node is the first lymph node that tumor cells encounter when trying to spread through the lymph.

When the sentinel node does not present tumor cells, we can assume that there will be no involvement in the rest of the axillary nodes.

To identify the sentinel lymph node(s), a radioactive substance and/or a blue dye are injected into or near the subareolar space. The substance or dye travels through the lymphatic ducts to the sentinel node or nodes. A lymphogammagraphy will be performed on the same day of the procedure to verify that the node or nodes have been marked.

The operating room surgeon will make a small incision in the armpit to detect and remove the sentinel node using a detection system (gamma probe). Subsequently, only those nodes marked with the radioactive substance or dye are removed and the pathology team analyzes and determines if there are cancer cells or not.

This technique significantly reduces the number of lymph nodes resected and reduces the risk of arm discomfort and the possibility of developing arm edema (lymphedema).

It is the removal of all the lymph nodes in the armpit. This gives us very precise information on the state of all the lymph nodes in the axilla, to know if they are invaded by tumor cells.
In addition to providing prognostic information, axillary lymphadenectomy continues to be the most effective method of controlling regional disease. Currently, it is continued when the sentinel node is positive and meets certain risk criteria.