Sentinel Lymph Node Biopsy

What are the axillary lymph nodes?

The axillary (arm pit) lymph nodes provide the main lymphatic drainage of the breast. To understand what this means, you need to understand what lymphatic fluid is. The heart pumps blood to the rest of the body (including the breast) through arteries. Most of the fluid in the blood returns to the heart through veins. A small amount of fluid stays in the tissues (including the breast) and returns to the heart through small clear channels called lymphatics. This lymphatic fluid goes through a series of lymph nodes to be screened for infection.

If breast cancer cells reach the lymphatics, they can be trapped by the axillary lymph nodes. Lymphatic fluid reaches a group of one to four lymph nodes first before reaching the rest of the axillary nodes. These are called the sentinel lymph nodes. Sentinel literally means “guardian” as these nodes “guard” the axilla.

What does a sentinel node biopsy involve?

In the past, treatment of any breast cancer involved removing all of the axillary nodes (axillary clearance). However, to reduce the chance of complications related to axillary clearance, we now perform a biopsy of the sentinel nodes first. This means we locate the sentinel node(s) with certain techniques then remove these nodes surgically. They are then sent to the pathology laboratory to be examined under the microscope. The results help us determine whether or not any further surgery to the axilla is necessary as well as guide adjuvant treatment such as chemotherapy and radiotherapy.

To locate the sentinel node(s), most surgeons use lymphoscintigraphy with or without Patent Blue Dye:

Lymphoscintigraphy is where a radio-labelled protein is injected into the skin of the breast around the areola which then travels into the lymphatics and gets trapped by the sentinel node(s). A radio-labelled protein is a protein that has been labelled with a very small dose of radiation (safe even for pregnant women at a reduced dose).

A lymphoscintigram may or may not be done afterwards. It is an imaging test that shows where the lymph node is and whether a number of nodes have been detected.

In the operating theatre, a so called “gamma-probe” is used to listen to the signal from the sentinel node(s). This auditory signal guides the dissection during surgery.

The injection is done under local anaesthetic or no anaesthetic as the needle is very small and the pain associated with injection is similar to that associated with a local anaesthetic.

The timing of the injection needs to be a few hours before surgery:

  • For an afternoon procedure, this is in morning of the day of surgery.
  • For a morning procedure, this can be done the afternoon before.

Patent Blue Dye is a blue dye as the name implies which is injected under the skin of the breast around the areola just before your surgery under a general anaesthetic.

Once again, the dye travels in the lymphatics and is trapped by the sentinel node(s) making them blue. This can help identify the lymph node visually during the surgery.

The dye is safe but can carries a 1 in 1000 risk of a severe allergic reaction.

There may be a blue tinge under the skin for some months after surgery and you may pass green urine for the first two days as the dye is excreted in the urine.

Under general anaesthetic, a small incision is made over the bottom of the hair-bearing area of the axilla. Using the auditory and visual signals, the sentinel node is dissected out. Dissection continues until the gamma probe signal is less than 10% of the original sentinel node signal. The average number of sentinel nodes is between 2 and 3.

After injection of local anaesthetic, the wound is closed with dissolving sutures.

What are the risks of surgery?

The risk of significant bleeding from an sentinel node biopsy is small.

The risk of infection from a sentinel lymph node biopsy is small and is further reduced by giving prophylactic antibiotics at the start of the procedure.

The commonest complication of a sentinel node biopsy is a small collection of inflammatory fluid called a “seroma”. Although unlikely, this may require drainage which is a simple procedure that is painless and is carried out in the office without the need for any anaesthetic.

Nerve damage is unlikely as the area dissected is limited to the lymph nodes. There is a theoretical risk of damage, however, to the nerves that course through the axilla.

There are a number of nerves that course through the axilla. Three of these nerves supply muscles and if damaged may cause weakness of these muscles resulting in weakness of arm movement or so-called “winging” of the scapula. Thankfully, damage to these nerves is rare as dissection is done very carefully to preserve these nerves.

Another nerve is a sensory nerve called the intercosto-brachial nerve which supplies sensation to the inside of the arm. This nerve is preserved during a sentinel node biopsy.

Perhaps the most troublesome complication of any surgery on the axillary nodes is arm lymphoedema. This results from interruption of the lymphatic drainage of the arm as the arm is also drained by the axillary nodes.

The risk of severe lymphoedema from a sentinel node biopsy is only 1% which is one of the main advantages of this technique over a full axillary clearance.

After axillary surgery, it is important to mobilize the shoulder gently to avoid getting a stiff shoulder. This is much less likely than with an axillary clearance.

Before surgery

Fast from midnight for a morning procedure OR from 7am for an afternoon procedure.

You will be booked for the lymphoscintigram as mentioned above – the morning of surgery for an afternoon procedure, or the afternoon before for a morning procedure.

You may also be required to have a radiological procedure such as the placement of a guidewire for your breast surgery. This will be co-ordinated with your lymphoscintigram.

You will be informed of your admission time which will depend on the above.

After surgery

Pain is usually minimal after a sentinel node biopsy.

You should take regular Panadol (as long as there are no medical reasons for you not to take it such as an allergic reaction or liver disease).

Non-steroidal anti-inflammatory medication such as Neurofen and Voltaren can also help with pain and inflammation but should be taken on a full stomach. Take these for the first 3-5 days as required.

Stronger pain killers such as opioid anaelgesics (Endone, Codeine) are usually not required and should be taken sparingly as they can cause constipation.

The wound is dressed with Dermabond glue which is waterproof. The glue feels hard which is normal. It sheds off over the 2-3 weeks.

You can go home the same day unless other procedures are performed at the same time which may require overnight admission (such as a mastectomy).

You will be followed up within 1-2 weeks of your surgery to review the wound and discuss pathology of the lymph node(s).

Your follow up appointment is usually made for you prior to discharge.

A positive lymph node requires further staging of the cancer with more imaging. It may mean further axillary surgery is required and may also affect the decision regarding adjuvant chemo or radiotherapy.