Sentinel Node Biopsy
Lymph nodes and Lymphatics
Lymph nodes are small gland that filters the natural body fluid (serum). The fluid is collected from the tissue into the nodes via small channels called lymphatics. Lymph nodes are found almost everywhere in the body. There is a large group of nodes in the axilla (arm pit) that drains the corresponding breast and upper limb.
At a certain stage the cancer cells will assume the capability of travelling outside the primary site, this spread takes place through different pathways. Breast cancer tends to travel through the lymphatics, thus can be picked up by the lymph nodes. Other pathways of travel are through blood stream and nerve sheeths.
Sentinel Node Studies
A Sentinel Node Study is mapping of the sentinel lymph node/s. The sentinel node is the first node filtering the natural fluid away from the area of concern that your breast “drains” to.
The aim is to look for the spread of cancer cells outside of the breast. The sentinel lymph node is more likely than other lymph nodes to pick up the cancer cells. If this node is clean, it is likely the other nodes have not been affected. The test is accurate in 95% of the time.
Sentinel node biopsy
Sentinel node biopsy is removal of the node(s) done by the surgeon during breast surgery (breast conserving surgery or mastectomy). Sometimes it may be performed as a separate procedure. Usually there are one to three sentinel nodes; the most common location is in the axilla. Sometimes the sentinel node is in another part of the body.
How is the sentinel node found?
There are two ways of finding the sentinel node. The surgeon will use one or both techniques. These are:
Mapping by Nuclear medicine (lymphoscintigraphy). This is done via an injection of a low-grade radioactive fluid (isotope) into the breast. The radioactive material will travel through the lymphatics and will be picked up by the nodes. This procedure is either done the afternoon before or the morning of your operation. The surgeon during the operation will use a hand held type of Geiger counter called a gamma probe; that detects the radioactivity in the nodes and will be able to direct the surgery towards these nodes. The amount of radioactivity produced by the tracer is very minimum and does not usually cause risk to the person or others. If you had the injection in the evening it might be advisable not to get close to young children for prolonged periods of time that evening.
A Patent Blue dye study, performed during the surgery by injecting a blue dye into the breast. This is done after you are anaesthetised. The blue dye will travel to the lymph nodes via the lymphatic vessels and the sentinel lymph node(s) should turn blue.
Alternatively, the blue dye or the radioactive fluid can be used alone to look for the sentinel node.
What does the procedure involve?
You will be advised when to attend the nuclear medicine session, you will have injections of radioisotop into the breast. A series of pictures is then taken to show where the sentinel node/s is located. The area is marked on your breast with a special pen. When this is completed you will be directed to the theatre. At surgery, the anaesthetist will put you to sleep and the surgeon will give you the blue dye injections. During the operation the blue dye and radioactive material will show the surgeon to which lymph node(s) breast cancer cells are most likely to travel. The surgeon can see the blue sentinel node(s) and detect the radioactive substance using the gamma probe he then removes the sentinel node(s).
If more than one sentinel node is found, all the sentinel nodes are removed. If another enlarged lymph node in the armpit is found without dye in it, the surgeon will usually remove it as well. If the sentinel node is not in the armpit, the surgeon will remove it if this can be done safely.
The Pathology tests
The sentinel nodes are examined by a pathologist. Usually two tests are done on the nodes; a quick test which gives the answer during the operation; while you are still asleep, the second test is a more thorough, it will take around 5 days before the results are finalised. This second test is the final more accurate test.
If there are cancer cells in the sentinel node, further surgery (axillary dissection) may be needed to remove more lymph nodes from the armpit to check how many lymph nodes are affected. If the sentinel nodes are examined during surgery, it may be possible to remove the remaining lymph nodes during the same operation. However, if the cancer is detected in the second test then a second operation is needed few days later. In a small number of cases, it is not possible to find the sentinel node at the time of surgery. In this situation, an axillary dissection may be recommended.
Advantages of having a sentinel node biopsy?
Clinical trials have shown that sentinel node biopsy is associated with a lower risk of arm problems than axillary dissection. This mean the risk of numbness, shoulder stiffness and lymphoedema is lower than with axillary dissection.
Strategic removal of just one or a few key underarm nodes can accurately assess overall lymph node status in women who have relatively small breast cancers (no more than two centimetres) and who have lymph nodes that don’t feel abnormal before surgery.
Studies have shown that after almost five years, women who have had just the sentinel node removed were as likely to be alive and free of cancer as women who had more lymph nodes removed.
Side effects of sentinel node biopsy?
There will be some discomfort associated with sentinel node biopsy, and the injection of radioactive isotope sometimes stings. The sentinel node biopsy might require a small but different wound than the primary breast wound.
The small amounts of blue dye or radioactive tracer usually disappear from the system in 24 – 48 hours. There’s a small risk of allergic reaction to the solutions however allergic reactions are usually mild and easily treatable. Severe reactions are extremely rare.
If blue dye is used to find the sentinel node:
Your urine may turn blue-green for 24 hours after surgery.
The skin of the breast may also become blue. This will fade with time but may take up to 12 months to disappear completely.
You may get blue coloured bowel motions.
Is the sentinel node biopsy always accurate?
In a small number of women (5%), the sentinel node doesn’t have cancer cells, even though there are cancer cells in the other lymph nodes in the armpit. This is called a ‘false-negative result’. A false-negative result sometimes occurs because lymphatic vessels running to the lymph nodes that have cancer cells in them are blocked by the cancer; the dye goes into other lymph nodes instead. This happenes in less than 5% of cases.
Mr Falah El-Haddawi