Anatomy-Lexicon

Sentinel lymph nodes

definition

A sentinel lymph node is the lymph node that comes first in a lymphatic drainage area of a tumor.

When tumor cells spread via the lymphatic system, these cells first settle (metastasize) in the sentinel lymph nodes. If this lymph node is therefore not involved, it can be assumed with a high degree of probability that there are no further metastases or that the tumor has not yet spread.
The sentinel lymph node plays an important role in breast cancer and malignant skin cancer.

anatomy

Lymph nodes are distributed throughout our body. A distinction is made between regional lymph nodes and collective lymph nodes: regional lymph nodes receive the lymph directly from the organs and collective lymph nodes take up the lymph from several regional lymph nodes.
The sentinel lymph node is the first lymph node in the drainage area of a tumor. Depending on where the tumor is located, the sentinel lymph node may be in a different location in the body. There are many lymph nodes around the chest, especially near the armpits. If the tumor is on the side of the chest, the sentinel lymph node is slightly above in the direction of the armpit. It is the first lymph node that is affected via the lymphatic pathway when breast cancer has metastasized, as it is directly connected to the tumor via a lymphatic vessel.
However, this tiny lymph node is not in the same place in every woman and can be difficult to find. To identify the sentinel lymph node, dye solution or radioactive substances can be administered, which can then be seen by means of the dye or with the aid of a radiation detector.

Lymph nodes are usually up to an inch in size. The size can vary depending on the level of activity. Lymph nodes can swell painfully if they have to protect the body from foreign bodies, for example if they have a cold.
Even with malignant changes, lymph nodes can be enlarged. In this case, however, they are usually not painful and difficult to move against the surrounding tissue.

function

Lymph nodes are the filter stations of the lymphatic system. The lymph is transported from the tissue and organs to the lymph nodes via the lymphatic system. There, foreign bodies are discovered by the immune system and can thus be fended off. Tumors can also form settlements (metastases) in the surrounding tissue via the lymphatic system. Depending on the extent of the metastasis, the prognosis of the disease can be better or worse. In addition, the extent of the metastasis can influence the choice of therapy.

Sentinel lymph nodes are normal lymph nodes which, however, are primarily located within the lymphatic drainage area of a tumor. They have the same function as other lymph nodes and act as filter stations. If tumor cells spread via the lymphatic system, they first accumulate in the sentinel lymph node.

The sentinel lymph node is particularly important in breast cancer and malignant skin cancer. In other types of cancer, the lymph flow flows in several directions, so that no statement can be made about a single sentinel lymph node. If a tumor is surgically removed, the sentinel lymph node is usually also removed. It plays a role in the further prognosis of the disease. Since a small sentinel lymph node can be difficult to identify, it is possible to visualize the lymph node you are looking for using staining or radioactive substances. After removing the sentinel lymph node, it is examined. If it is free of tumor cells, the likelihood that the tumor has metastasized via the lymphatic system by this time is low. In this case, it may be possible to dispense with removing other subsequent lymph nodes. In this way, any discomfort that may arise from radical lymph node removal can be prevented.

Nevertheless, despite the lack of evidence of tumor cells in the sentinel lymph node, settlements may be present in the subsequent lymph nodes. One speaks of so-called "metastasis jumps". If tumor cells are found in the sentinel lymph node, the probability is high that further settlements of the tumor are present in the surrounding lymph nodes and these must also be removed. Correspondingly, the possible detection of tumor metastases in the sentinel lymph node can be of therapeutic as well as prognostic significance.

Removal of the sentinel lymph node and subsequent lymph nodes may prevent further spread of tumor cells. If the tumor has not metastasized any further by this time, a good prerequisite can be created with the complete removal of the tumor, the sentinel lymph node and the subsequent lymph nodes.

If you have breast cancer

In breast cancer, the sentinel lymph node examination plays an important role. Because breast cancer often settles in the surrounding lymphatic system, the sentinel lymph node involvement is a good way of assessing the extent to which it has spread.

Most of the lymphatic drainage area of the breast is in the armpit. The corresponding lymph nodes are also located there. The sentinel lymph node is found just before the large cluster of axillary lymph nodes. It can be surgically removed and examined for tumor infestation: with a tumor-free sentinel lymph node, the likelihood that the tumor will have settled via the lymphatic system by this time is low.

Read more about the topic here: Metastasis in breast cancer

Nevertheless, even with breast cancer, it is possible that, despite the lack of evidence of tumor cells in the sentinel lymph nodes, subsequent lymph nodes are affected. One speaks of so-called "metastasis jumps".

If tumor cells are found in the sentinel lymph nodes, the subsequent lymph nodes in the armpit should also be surgically removed. Radical removal of lymph nodes can prevent the tumor from spreading further through the lymphatic system. However, this procedure can lead to complications such as nerve damage. In addition, lymphedema can develop due to an impaired lymph drainage.

What is the prognosis for breast cancer if the sentinel lymph node is affected?

The prognosis generally depends on the extent of the primary tumor as well as its complete removal. The spread of tumor cells in lymph nodes worsens the prognosis of the cancer somewhat, since the likelihood of the tumor spreading via the bloodstream is high.
If the sentinel lymph node in breast cancer is affected by tumor cells, the prognosis depends on how many of the subsequent lymph nodes are also affected. Since the tumor spreads via the sentinel lymph nodes into the downstream lymphatic system and the lymph nodes contained therein, a prognosis cannot be made automatically.

In breast cancer, the tumor spreads mainly to the armpit lymph nodes. If the sentinel lymph nodes are affected, these lymph nodes should therefore be surgically removed. After such an evacuation, the removed lymph nodes should be examined for tumor cells. After the examination, the decision on the appropriate therapy and a more precise prognosis of the disease should be easier to assess.

You can find out more about the topic here:

Lymph node involvement in breast cancer
Prognosis in breast cancer

Sentinel lymph nodes in skin cancer

As with breast cancer, the sentinel lymph node is of great importance in malignant skin cancer. Here, too, the sentinel lymph node is the first lymph node in the respective lymph node station. If this is tumor-free, the probability that there are further settlements in the surrounding tissue is low. However, if tumor cells can be detected, the lymph nodes of this lymph node station should be removed (lymphadenectomy) to reduce the risk of further spread.

Read more about the topic here: Skin cancer treatment

What happens if the sentinel lymph node has to be removed?

If a sentinel lymph node is infected with tumor cells and it and possibly subsequent lymph nodes have to be removed, symptoms may arise after the operation. The complications vary depending on the location and extent of the removed lymph nodes. In general, bleeding and wound healing disorders can occur.

Removing the lymph nodes can cause what is known as lymphedema. It occurs when the operation causes a blockage of drainage in the lymphatic system and the lymph can no longer be properly removed. Lymphedema is thus an accumulation of fluid in the intercellular space and presents itself as a visible and palpable swelling.

If the lymph nodes in the armpit are removed in breast cancer, nerve injuries can also occur, as many nerve pathways run in this area.

Guardian lymph nodes of the groin

Sentinel lymph nodes in the groin can, for example, be decisive in skin cancer that is located in this area. There is a large collection of lymph nodes in the groin. If the sentinel lymph node is affected, it may be necessary to remove the lymph nodes there as well. They can be removed under local or general anesthesia. In the case of other types of cancer, too, lymph nodes in the groin can contain tumor deposits and removal (lymphadenectomy) can be useful.