The sentinel lymph node is the first lymph node to which a cancer will most likely spread from its point of origin. They are usually found in the nearest lymph node station. For example, a melanoma of the leg may spread to the lymph nodes of the groin whereas one of the face may go to lymph nodes in the neck.
A lymph node is a bean-shaped organ that is part of the body’s immune system. They contain white blood cells that help the body to fight infection. There are hundreds of lymph nodes throughout the body connected by tiny channels called lymphatic vessels. Lymphatic fluid is filtered through these nodes and an immune response is mounted against any foreign material (e.g. bacteria or viruses) in that fluid. Lymph nodes tend to be found in clusters in particular parts of the body such as the neck, armpits (axillae), groin, chest and abdomen. Many kinds of cancers can spread through the body via the lymph nodes.
A sentinel lymph node biopsy is removal and pathological analysis of the sentinel lymph node in order to determine if cancer has spread to it. A negative sentinel lymph node biopsy indicates that the cancer has not spread. A positive sentinel lymph node biopsy indicates that the cancer has spread and may involve other nearby lymph nodes and/or other organs.
First the sentinel lymph nodes must be located. On the day of, or day prior to the sentinel lymph node biopsy, a nuclear medicine physician will do a study called a lymphoscintogram. This does not require an anaesthetic. It involves injecting radiolabelled dye into the tumour site and then mapping to which lymph node(s) that dye goes. X-rays are taken and will be given to you to take to your operation. The radiolabelled dye in the sentinel lymph node remains detectable at the time of operation.
At the operation, once you have been anaesthetised, the surgeon will then inject blue dye into the tumour site. Like the radiolabelled dye, this also drains to the sentinel node and will turn it blue. At this point the sentinel lymph node is now radioactive and a blue colour.
Using the lymphoscintogram as a map and a sentinel lymph node probe as a radioactive detection device, the surgeon will go looking for a radioactive, blue sentinel lymph node. That node or nodes will be removed and sent to the laboratory for analysis.
Under the same anaesthetic, the primary tumour is also usually removed.
Sentinel lymph node biopsy is a highly sensitive way of determining cancer spread – far more sensitive than any scan. If it is negative for cancer, a patient may be able to avoid more extensive lymph node surgery (or other therapy), reducing the potential complications of having those lymph nodes removed.
Sentinel node biopsy is not useful in all types of cancer. It was first used in penile cancer and is most often used to stage breast cancer and melanoma. It is also used for endometrial cancer and a few sarcomas including rhabdomyosarcoma, and epithelioid, synovial and clear cell sarcoma. Other cancers being investigated include cancers of the head and neck, vulva, cervix, colon and rectum, stomach, oesophagus, thyroid and lung.
Prior to your operation you may need to attend a Preadmissions Clinic. Your fitness for surgery will be assessed, tests may be ordered and referrals to other specialists arranged if required.
You cannot eat for 6 hours prior to your operation. You may sip water for up to 2 hours prior to your operation. Fasting decreases the risk of vomiting and aspiration during induction of anaesthesia. Aspiration can cause pneumonia and a prolonged stay in hospital.
Sentinel lymph node biopsy is done under general anaesthesia. You will be asleep during the whole procedure. The anaesthetist will discuss the anaesthetic with you prior to your operation. They will see you in the pre-operative area and accompany you to the operating theatre.
Following general anaesthesia, you are positioned on the operating table, the incision site is marked, and local anaesthetic is injected to decrease post-operative discomfort. Blue dye is then injected around the tumour. A skin incision is made over the nodal basin of interest. Using the lymphoscintogram as a map, the sentinel lymph node probe is used to direct the dissection and, disturbing as little lymphatic tissue as possible, a blue-coloured, radioactive lymph node is sought. Once found, it is removed. The sentinel lymph node probe is used to measure how radioactive the node is and then directed back to the lymph node basin. If the radioactivity count in the lymph node basin is <10% of the sentinel lymph node, the procedure is concluded. The skin is closed with absorbable sutures and dressed with a waterproof dressing. Occasionally there is more than one sentinel lymph node. They can occur in the same or a completely different lymph node basin. All sentinel lymph nodes must be removed, even if it means that two separate lymph node basins are operated on.
In the case of a melanoma, the primary tumour is removed following the sentinel lymph node biopsy.
Following the operation, you will wake up in the recovery area. You will feel a little disoriented and may feel a little nauseous. The staff in recovery are equipped to help you. Immediate post-operative pain is usually minimal. Once you are awake and oriented, you will be taken to a ward bed. After a few hours, and once the nurses are satisfied that it is safe, you can get out of bed.
There are no dietary restrictions or special dietary supplements that are required after sentinel lymph node biopsy. You may eat whatever you choose. Oral analgesia including paracetamol is usually all that is required for pain relief. You may bathe and shower. The wound is waterproof and can get wet.
You should avoid strenuous physical activity for two weeks after your operation. It increases the risk of post-operative bleeding which could result in a trip back to the operating theatre. Once this period has passed and you feel that you have recovered, you may return to your normal physical activities.
Post-operative swelling around the wound is normal and usually resolves within a month or so. No specific wound management is needed in the first two weeks while the dressings are on. After this, gentle scar massage is advisable for 10 minutes two or three time a day for 6 months. You may use whatever moisturising lotion you like (e.g. sorbolene, bio-oil etc.) but creams with Vitamin E should be avoided for the first post-operative month. Alternatively, you can keep the scar covered with a silicon strip for 12 hours a day for 6 months. These strips are available from the chemist but are quite costly.
Initially the scar will be pink. Over 6-12 months, the scar will fade until it becomes pale.
This occurs in <5% patients and is usually self-limiting. Occasionally a return to theatre is required for evacuation of blood clot from the wound.
These can complicate any type of surgery and can usually be treated with a short course of oral antibiotics. Uncommonly, IV antibiotics or further surgery is required.
This is a lump that is created by a collection of lymphatic fluid that has leaked out of disrupted lymphatic channels following the sentinel lymph node biopsy. They usually resolve spontaneously. They should be aspirated if they become uncomfortable. Occasionally they can get infected and then a return to the operating theatre may be required to evacuate the infected fluid.
Rarely patients can have an allergic reaction to the blue dye used in sentinel lymph node biopsy. This becomes apparent intraoperatively and the anaesthetist will be prepared to deal with it.
Numbness or Tingling
This may occur if nerve supplying sensation to the skin are disrupted during the operation. It is usually temporary but is occasionally permanent.
False Negative Biopsy Result
This is where a sentinel lymph node biopsy is reported as negative even though cancer cells have spread to the regional lymph nodes or other parts of the body. It gives the patient and the doctor a false sense of security. This occurs in <5% patients.
Lymphoedema is swelling that is caused by accumulation of lymphatic fluid within the tissues. It is an uncommon complication of sentinel lymph node biopsy that arises due to disruption of the lymphatic vessels. It usually affects limbs. The area affected may swell to a variable degree. Mild cases are barely noticeable. Severe cases can severely impair limb function and the overlying skin may become thickened or hard. In addition, the affected area is at risk of infection. The chance of this occurring due to sentinel lymph node biopsy is <5%.
A follow-up appointment should be arranged in rooms 2 weeks after your operation for a discussion regarding pathology. At this appointment, your wounds will be assessed, and any further investigations and management arranged.
There is no specific law covering surgery and driving. It is not advisable to drive immediately after surgery. In general, in order to return to driving, you must:
This pamphlet is intended to provide you with information and does not contain all known facts about sentinel lymph node biopsy. Treatment may have uncommon risks not discussed in this pamphlet. Please do not hesitate to ask any questions you may have.