Sentinel Node Biopsy

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WHAT IS SENTINEL NODE BIOPSY? The sentinel node biopsy is also known as the “Sentinel Lymph Node Biopsy (SLNB)“. It is a procedure that involves the surgery of a patient having cancer which in most cases are breast and melanoma. It indicates the depth to which cancer has infested a patient in the lymphatic system…. Read More

Sentinel Node Biopsy


The sentinel node biopsy is also known as the “Sentinel Lymph Node Biopsy (SLNB)“. It is a procedure that involves the surgery of a patient having cancer which in most cases are breast and melanoma. It indicates the depth to which cancer has infested a patient in the lymphatic system.

The sentinel node biopsy searches for sentinel nodes that might have been drained by a tumor. A tracer material is injected to extract the sentinel nodes for further examination in the laboratory to conclude cancer cells that may be present. 

After the test, the absence of cancer indicates that there is no cancer in the lymph nodes, therefore, no need for further extraction of the lymph nodes. But, if the case is reversed and cancer is present, more lymph nodes will be required to be removed. These nodes are little and they filter fluids in the patient to keep the body healthy. They contain a substance known as lymph, as the lymph circulates the body, bacteria, infections and cancerous cells are trapped


The sentinel lymph node biopsy is necessary for patients with possible cancer to deduct a spread into the lymphatic system. The sentinel node biopsy is commonly used for patients with melanoma and breast cancer. Other cancers may include:

  1. Non-small cell lung cancer.
  2. Thyroid cancer.
  3. Stomach cancer.
  4. Colon cancer.
  5. Head and neck cancer.
  6. Esophageal cancer.

When a patient has melanoma skin cancer, cancer tends to spread immediately into the lymph nodes.


The sentinel lymph node biopsy can be done on anyone possessing any of the above cancers, though it has more occurrence in females.


It is required of the patient to avoid food or water intake for some time before the test in case of a reaction with the anesthesia. The patient is to wear a comfortable cloth and drop any valuables or jewelry at home.


Sentinel lymph node biopsy involves the usage of radioactive tracers to locate the sentinel nodes. The procedures are categorized into the process before undergoing the surgery, the process during the surgery and what to do after the surgery is completed. 

  • Before the Procedure:

The operation commences with the location of the sentinel nodes in the body and there are two methods of achieving this. The first is the radioactive solution injection while the second method is the blue dye injection. 

These methods are explained below:

  • Radioactive Solution:

For this method, an injection of a low concentrated radioactive substance is administered to the patient close to the tumor. The radioactive material goes into the lymphatic system and locates the sentinel nodes. 

This radioactive injection is performed few hours to or even a day before according to the recommendation of the doctor to extract the sentinel lymph nodes.

  • Blue Dye Injection:

The blue dye is a harmless substance that is injected into the system also close to the tumor. The blue dye is circulated through the lymphatic system to the sentinel lymph nodes affecting the color by making them have a lighter shade of blue. 

The color of the patient’s skin where the blue dye was injected might change color but it can be permanent in some cases though. Then the urine turns out blue for a short period. Unlike the radioactive solution, the blue dye is injected just before the sentinel lymph node biopsy to extract the sentinel lymph nodes.

According to research, some doctors tend to use both the radioactive solution and the blue dye injection together to effect the removal of the sentinel lymph nodes. 

Though, it is dependent on the doctor’s preference. The process of locating the sentinel nodes in the system is known as the “Sentinel Lymph Node Mapping”.

  • During the Procedure:

After the radioactive solution or blue dye has been injected into the patient near the tumor and the sentinel lymph nodes have been located, the patient will be placed under anesthesia to calm the nerves and make the patient unconscious after which an incision will be made just over the region where the lymph nodes are present.

The material injected to extract the lymph nodes determines the procedure for the surgeon to undergo. When a blue dye is injected into the lymphatic system, the color of the sentinel lymph nodes is tagged blue enabling the doctor to identify with them. 

But when the radioactive material is used several hours to the commencement of the operation, a gamma detector is used which is inserted into the little incision made by the surgeon. This gamma detector senses the accumulated radioactivity and identifies the sentinel nodes. After the sentinel lymph nodes have been identified, they are removed from the lymphatic system. A patient can possess a sentinel lymph node of about 600, though some are extracted. 

Then, the sentinel lymph nodes are delivered to a pathologist for examination whose duty is to examine for cancers present with the aid of a microscope. 

In few cases, cancers can be removed while performing the SLN surgery while in some cases the sentinel lymph node biopsy is performed just before or after the removal of cancer from the system.

  • After the Procedure:

After the surgery has been performed, the patient is taken to the recovery room where the specialist monitors the recovery rate and complications that may be present to proffer solutions. 

Further surgery might be required depending on the result but if not, the patient can be discharged that same day.


The test result deducted determines whether any other surgery is to be carried out. The absence of cancer in the sentinel nodes means that there is no need for further surgery or test, though the doctor might draft a treatment program in case one is required. 

If the report indicates the presence of cancer in the sentinel nodes, then, it may be recommended that more lymph nodes are removed to determine the quantity of the lymph nodes infected by cancer.

The test result can take a week to be out but in some cases, the pathologist can simultaneously observe the nodes while operating on the patient and if cancer is present, more sentinel nodes will be extracted at once instead of undergoing another operation.


Sentinel lymph node biopsy has few risks involved with just complications which are listed below:

  1. Lymphedema:

This is a rare complication associated with the sentinel lymph node biopsy as it results in swelling and fluid accumulation due to inadequate draining of lymph fluid from a region in the patient by the vessel. 

This is feasible if most of the lymph nodes are removed from just one region in the body.

  1. Bruises or feelings of pain in the region operated.
  2. Possible infection.
  3. Possible reaction to the blue dye or radioactive solution.
  4. Bleeding.

It takes about two weeks for a patient to recover after the sentinel lymph node biopsy has been conducted on a patient.


A well-trained surgeon is liable to perform this surgery but it is conducted with the aid of the pathologist and health team care.


The sentinel lymph node biopsy is expensive and it ranges from $696,600 and $1,051,100 US dollars. Performing the surgery with a wide excision costs about $69,000 to $120,100 US dollars.


  • What is the difference between sentinel and axillary lymph nodes biopsy?

The sentinel lymph nodes are used for patients with breast cancer at a later stage while the axillary lymph node biopsy is currently the best for the early stages of breast cancer.

  • How accurate is the sentinel node biopsy procedure?

The sentinel node biopsy has an accuracy of about 96% making the surgery effective for determining breast cancer and melanoma. It has a sensitivity rate of 92% and the false-negative result is attributed to the tumor greater than 0.05m.

  • How painful is sentinel lymph node biopsy?

In most cases, the only pain felt is as a result of the small incision made in the body probably the underarm or breast but over a short period, the pain stops.

  • Do lymph nodes regenerate after removal? 

Over a year, the lymph nodes tend to regenerate and replace the extracted ones. Therefore, relieving the patients of lymphedema and reducing accumulated fluid.

  • Is the axillary lymph node dissection necessary?

The axillary lymph node dissection is performed only when more than two sentinel lymph nodes contain cancer.