Sentinel (Blue) Lymph Node Biopsy

Cancer surgery aims to excise primary tumors as well as metastatic sites (areas where the cancer may have spread). The most common metastatic sites are the regional lymph nodes. In particular, the axilla (armpit) is a lymph node basin for breast cancer. The information gained from removing and analyzing lymph nodes from the armpit assists in staging the breast cancer and helps to inform the decision about further treatment, such as chemotherapy.

In the past, patients diagnosed with breast cancer that was suspected to have spread to the lymph nodes had a full dissection (complete removal of all of the nodes) of the suspected lymph node basin. This occasionally resulted in complications such as infection, wound breakdown, seroma (a fluid collection that can be uncomfortable) and, infrequently, lymphedema (swelling of the arm). The sentinel (blue) node biopsy enables an accurate diagnosis of the suspected lymph node without the more-invasive full dissection.

In the sentinel (blue) node biopsy, the first node in a basin is identified as the sentinel lymph node (SLN) because it has been proven to be the area where the cancer first spreads. If there are no tumor cells seen in the SLN, it means there is only a very small risk that tumor cells have traveled to the other lymph nodes in the basin. This SLN can be located by injecting a special blue dye or radioactive substance near the nipple, around the cancer or biopsy area. These substances have the right particle size so that they are taken up by the lymphatic system and will color the first node – the SLN.

If cancer cells are breaking off the primary tumor, they will travel to this first node, carried by the lymphatic vessels (which transport fluids from tissues into the bloodstream). If the cancer has spread from the breast tumor, this is the lymph node most likely to contain a metastasis (cancer). This knowledge enables our surgeons to remove only those lymph nodes that are more likely to harbor cancer cells. If the sentinel node is found to contain cancer, additional lymph nodes may have to be removed. If it is free of cancer, additional lymph node surgery may be avoided.

Certain lymphatic mapping techniques may be applicable to your case, including:

Preoperative Lymphoscintigraphy

This technique involves obtaining a preoperative lymphoscintigram to image the basins at risk for metastatic disease and provide a roadmap for the surgeon. Lymphoscintigraphy is performed under the direction of a radiologist who specializes in nuclear medicine. The actual tumor or cancer site is injected with a special protein that is labeled with a trace amount of radioactivity – no more than what is produced by routine chest X-rays or mammograms. No adverse reactions have been reported to the injection of this radio-labeled protein. The protein flows through the lymphatic channels toward the lymph node basins, enabling an X-ray image to be obtained of the basins into which tumor cells migrate. The surgeon can then use a radiation detector during surgery to pinpoint the lymph node that has the highest radiation counts.

Intraoperative Lymphatic Mapping

In this technique, patients are injected intraoperatively with a blue dye (lymphazurin or methylene blue) around the nipple or primary breast cancer site. The dye is then absorbed by the lymphatics. After the injection, a small incision is made in the armpit to search for the sentinel node or nodes. Blue-stained lymphatic channels are identified and followed to the sentinel node(s). One or more SLNs are then removed and submitted to pathology for evaluation. All blue staining nodes, or "hot" nodes (nodes with high radioactive counts), are removed and called sentinel nodes.

Patient Eligibility

Not everyone is a candidate for sentinel (blue) node biopsy. These procedures are not recommended for patients with suspected spread of the cancer to the lymph nodes based on physical examination or imaging, or with lymph nodes that have been biopsied before surgery with confirmation that the cancer has spread there.

Possible Side Effects

Lymph node biopsy surgery always produces some postoperative discomfort for about a week. Swelling or fluid builds up under the incision and can remain for several weeks. Infection is uncommon, but can develop up to seven days later. The most serious complication of any procedure involving the lymph nodes is lymphedema. The risk of lymphedema with a sentinel lymph node biopsy is less than 7 in 100. 


With its low complication and accuracy in staging, SLN biopsy is the best option for patients with early breast cancer. If no tumor is found after careful analysis of the SLN, there is no need to complete the dissection to remove more nodes. This significantly reduces the risk of lymphedema.