Sentinel Node Biopsy

What are Lymph Glands or Lymph Nodes?

Lymph nodes are oval-shaped glands that contain cells that defend the body against foreign substances. 

The lymphatic system is a structure of lymph vessels and lymph glands throughout the body which play an important role in the body's mechanism of fighting infections and tumours. 

The lymphatic system involves tiny channels that carry fluids and debris to the lymph nodes/glands, which act as filters. Groups of lymph nodes are in the neck, ears, underarms, chest, abdomen, and groin. 

The lymph nodes that filter waste fluid and cells from the breast are mainly located in the armpit (also called the axilla).

These lymph nodes are usually the first ones affected if cancer spreads beyond the breast. The number of lymph nodes in the axilla varies from person to person but usually ranges from around 20 to 40.

What is a Sentinel Lymph Node?

The axillary sentinel nodes are the first lymph nodes to which cancer cells are most likely to drain cancerous fluid from the breast or to spread from a primary tumour. There are between one and three sentinel nodes.

What is a Sentinel Lymph Node Biopsy?

A sentinel lymph node biopsy is a procedure in which the sentinel lymph nodes are identified, removed, and sent for pathological examination to detect the presence of cancer cells. It is thought that if breast cancer cells escaped into the lymphatic system, they would travel to the sentinel nodes before moving on to other nodes. 

The Sentinel lymph node (SLN) technique is based on the study that tumour cells migrating from a primary tumour invade one or a few lymph nodes before involving other lymph nodes.

Sentinel lymph node biopsy is a minimally invasive technique proven reliable and accurate alternative treatment modality for breast cancer patients. During a sentinel lymph node biopsy, the surgeon removes only a few (1-5) sentinel lymph nodes.

Dissection of the sentinel nodes reduces the possibility of complications and, in most cases, provides the necessary information about cancer. If the sentinel nodes are free of cancer, it is assumed that the remaining nodes are also clear, and no further lymph nodes are removed.

Sentinel Node Sampling Benefits

After malignant breast cancer is identified, a Sentinel Lymph Node Biopsy offers an accurate and less invasive diagnostic procedure than the automatic removal of almost all axillary lymph nodes.

The biopsy is a less complicated procedure as there are fewer lymph nodes removed, minimises complications, and improves recovery time.

Indications for an Axillary Sentinel Lymph Node Biopsy

Sentinel node biopsy is recommended for patients who have early-stage breast cancer. 

Treatment for breast cancer usually involves removing some lymph nodes as well as removing cancer from the breast. 

Testing the lymph nodes is very important, as it gives you and your doctor information about the extent of breast cancer and helps to plan further treatment.

Why are Tumour Cells In Armpit Glands Important?

The status of axillary lymph nodes is one of the most important predictive factors in women with early-stage breast cancer. 

The axilla must be explored surgically and some lymph nodes removed and sent for pathological examination. Pathological examination of lymph nodes is the most accurate method for assessing the spread of disease to these nodes. The treatment plan for breast cancer is based on whether the lymph glands contain tumour cells.

Surgery (lumpectomy or mastectomy) in conjunction with axillary dissection/clearance is the best treatment option to remove the breast tumour. A significant number of lymph nodes are removed during the surgery. Lymphedema (localised fluid retention and tissue swelling) is a possible complication of the procedure.

How is the Sentinel Lymph Node Identified?

The following guides the surgeon in identifying the sentinel lymph nodes:

• Sentinel Node Imaging is a sophisticated lymphatic mapping that will be performed the day before or the day of surgery. A small amount of radioactive substance is injected into the breast that flows to the sentinel nodes through the lymphatic ducts and can be seen on a nuclear medicine scan (lymphoscintigram). Lymphoscintigraphy is used to find the sentinel lymph nodes that are removed and checked for tumour cells.
• Blue Dye Injection: Under general anaesthesia, a blue dye is injected into the breast. The dye flows through the lymphatic ducts to the lymph nodes. The first lymph nodes to receive the dye are removed and viewed under a microscope to detect cancer cells. It may not be necessary to remove more lymph nodes if the cancer cells are not found.
• Gamma probe detection: An intra-operative gamma probe (a highly directional Geiger counter) used in the operating room directs the surgeon to the radioactive isotope injected several hours before the surgery. The radioactive sentinel nodes are removed by the surgeon and investigated for cancer cells. 

Not necessarily all the lymph nodes that are mapped contain cancer cells. Rather, they are the first lymph nodes likely to be affected if cancer cells have escaped into the lymphatic system.

Does Sentinel Node Biopsy Indicate If I Need Surgery?

Sentinel node biopsy will not affect whether your tumour is suitable for lumpectomy (wide local excision) or mastectomy.

When is Sentinel Node Biopsy Performed?

Sentinel node biopsy is usually performed along with breast surgeries. Rarely it is done as a separate procedure before mastectomy when immediate reconstruction is preferred. 

A final pathological report of the sentinel nodes allows for a complete axillary clearance during breast surgery/reconstruction.

Based on the status of the sentinel nodes, one can decide about post-surgery radiation, which in turn influences the reconstruction decisions.

Care After a Sentinel Lymph Node Biopsy

Following the biopsy, you should keep your incision site dry for the first 24 hours. 

You may have some soreness and discolouration at the site due to the dye. Your doctor will prescribe pain medication to keep you comfortable. 

The discolouration will gradually fade away on its own. 

Risks With Sentinel Lymph Node Biopsy

As with any procedure, sentinel lymph node biopsy may be associated with certain risks and complications, such as 

• Pain, 
• Stiffness,
• Bruising or Swelling, 
• Infection,
• Fluid build-up and 
• Numbness or Nerve injury.

False Negative Biopsy Results

In some patients, the cancer cells are not seen in the sentinel lymph nodes, although they are present and may have already spread to other regional lymph nodes or other parts of the body. 

A false-negative biopsy result gives the patient and the doctor a false sense of security about the extent of cancer in the patient’s body.

False-negative SNB results may harm the treatment outcome for various reasons: missed nodes might lead to axillary recurrence that can be difficult to treat, diseased axillary nodes may be a possible source of distant metastases, and under staging affects decisions about systemic and specific radiation therapy to the breast, chest wall and nodal basins.

Sometimes, cancer cells may block the lymphatic vessels running to the lymph nodes that contain cancer cells and result in a false-negative report. In this case, the radioactive substance flows and stains the normal lymph nodes. A false-negative result can be avoided by removing the abnormal palpable nodes (not stained) during the surgery.

Multiple sentinel nodes are present in most breast cancer patients, and it is now accepted that cancer cells often drain directly to a group of nodes rather than to a single node.



Removal of sentinel lymph nodes is based on cherry-picking phenomenon leaving the axillary lymphatics in areas away from the sentinel nodes.