The sentinel node is the first lymph node to which the lymph from the neoplastic focus drains. Due to their location, metastases of malignant neoplasms spreading through the lymphatic vessels appear first in the sentinel node.
Sentinel node(sentinel node) is the first node in the drainage path of the lymph from an organ affected by a neoplastic disease. Lymph (lymph) is one of the body fluids, which is a filtrate that forms in almost every organ in our body. The lymph is transported by the lymphatic vessels. On the path of its flow there are lymph nodes whose task is to filter the lymph, i.e. to clean it of microbes. Lymph nodes catch bacteria and viruses flowing with the lymph. Unfortunately, this is also where cancer cells go, which can spread cancer throughout the body.
Sentinel node - what is it?
In oncological surgery, the diseased organ is often removed along with the nearby lymph nodes. The aim of this procedure is to reduce the risk of cancer cells, and thus disease, in other parts of the body, despite the removal of the primary tumor focus.
Removal of many lymph nodes has unpleasant consequences for the patient, which is best seen in the example of women after mastectomy. Women who have had all their lymph nodes removed from the armpit often suffer from lymphoedema of the entire arm due to the stagnation of the lymph. This complication affects about 10-20% of women. Lymph drains from the breast to the lymph nodes in the armpit, that is, the axillary nodes. There are from 20 to 30 nodes in the armpit, which are quite large (even up to 2 cm) and resemble a kidney in shape.
Sentinel node - when to remove?
Knowledge of lymphatic drainage has been used by oncologists and surgeons to develop less invasive methods of cancer surgery. Knowledge of the role played by the sentinel node prompted the idea to perform a biopsy in patients in whom it is possible before surgery.
Sentinel node removal makes it possible to assess whether the metastasis process has already started or not and whether the nodes can be left in a given patientarmpit.
Sentinel node biopsy is different than in the case of examining changes in the breast or other organs. This time, the lesion is not punctured with a needle, but the first 1-3 nodes are cut, only the first 1-3 nodes are removed from the lymphatic drainage path. The sample is submitted for histopathological evaluation so that the brain pathologist can check under a microscope whether it is necessary, in the case of breast cancer, to remove the remaining axillary nodes. If the presence of cancer cells in the sentinel node is found, its removal is necessary.
The absence of cancer cells in the first node gives almost 100% certainty that the next, higher lymph nodes also do not contain metastases, because there is no other way to them than through the sentinel node.
In patients after removal of only the sentinel node, with the remaining axillary nodes being saved, lymphoedema of the hand is much less likely to occur. A small scope of surgery is usually associated with less postoperative pain and a shorter recovery time.
Biopsy - removal of the sentinel knot
In the case of breast cancer, a small dose of the radiolabel (Technet-99) is injected into the patient before surgery. The marker is placed near the tumor. Administering a radioactive tracer is safer than standard X-rays. A blue dye (methylene blue) is then injected to facilitate the search for a node during the procedure. Now you have to wait for the marker to reach the sentinel node with the lymph.
Depending on the procedures adopted in the clinic, this may take from 1 to 8 hours. The patient goes to the operating room. The surgeon uses a special device called a gamma-camera to find the area where the sentinel node is located.
Gamma-camera beeps when its sensor is over the area where Technet-99 is concentrated. This is where the doctor makes an incision. In addition, its blue tint helps him identify the node he is looking for.
The removed knot or axillary nodes (sometimes there are even three "sentinels") is sent for histopathological examination. A pathomorphologist looks for cancer cells under a microscope.
After the treatment, the skin is discolored blue. Methylene blue is excreted in the urine over the course of the day. The urine is greenish in color The radioactive energy dissipates spontaneously, leaving no trace of radioactivity in the patient's body.
If the postoperative period is uneventful, the hospital stays at maximumone more day.
Another method of searching for the sentinel node is to inject indocyanine green into the area of the tumor. It is a substance that travels through the lymph vessels and stains the follicular structure of the lymph node green. The first stained node is the sentinel node, which is excised for histopathological examination to see if there are cancerous cells in it or not.
Sentinel node - presence of cancer cells
If, after analyzing the collected lymph nodes, it appears that they contain cancer cells, it is necessary to extend the operation and remove the remaining nodes, because most likely at least some of them already have breast cancer metastases.
Sentinel node - complications after biopsy
Most often, patients after sentinel node biopsy feel well and do not complain about postoperative complications. However, you may experience symptoms similar to those that occur after all the lymph nodes have been removed in the armpit. It is:
- pain
- lymphoedema
- nerves are sometimes damaged
The more nodes are removed, the more likely the above complications will occur.
Sentry node - growing role in diagnostics
Examination of lymph nodes is becoming increasingly important in diagnosing, treating and assessing the prognosis of patients in many neoplastic diseases.
Sentinel lymph node assessment is also used for other cancers such as:
- colorectal cancer
- esophageal cancer
- stomach cancer
Scientists are still working to improve the methods of examining the lymph nodes as less invasive as possible.
About the author
Anna Jarosz A journalist who has been involved in popularizing he alth education for over 40 years. Winner of many competitions for journalists dealing with medicine and he alth. She received, among others The "Golden OTIS" Trust Award in the "Media and He alth" category, St. Kamil awarded on the occasion of the World Day of the Sick, twice the "Crystal Pen" in the national competition for journalists promoting he alth, and many awards and distinctions in competitions for the "Medical Journalist of the Year" organized by the Polish Association of Journalists for He alth.