Overview of Axillary Sentinel Lymph Node Biopsy
Staging for breast cancer involves checking the local lymph nodes. The process of sentinel lymph node biopsy was created to examine the status of axillary lymph nodes without the need for a full axillary dissection. The idea behind identifying and removing sentinel nodes is that these nodes are the first to be affected if the breast cancer spreads to the lymph nodes. The careful examination of these nodes can provide information about the extent of cancer spread, which is crucial for predicting the course of the disease.
In the past, if a sentinel lymph node was found to be positive for cancer, it would trigger a full axillary dissection—removing all lymph nodes from the underarm area. However, recent studies suggest that this extensive procedure may not be necessary in all cases, even if a sentinel node is positive.
This is significant because axillary dissection is a complicated procedure and can lead to issues like lymphedema (swelling), nerve damage, ongoing pain, and lymphangiosarcoma (a rare form of skin cancer). Therefore, avoiding a full axillary dissection when a sentinel node is positive becomes an option if the patient has a small-sized primary tumor (T1 or T2) and fewer than three nodes involved with the tumor.
Anatomy and Physiology of Axillary Sentinel Lymph Node Biopsy
The axillary sentinel lymph node is usually found in fatty tissue in the area of the armpit, specifically in a place known as level I or level II lymph nodes. This area has lymph nodes also referred to as the pectoral (chest-related) nodes and clavicular (collarbone-related) nodes by medical professionals. The fatty tissue in this area, or axillary fat pad, lies deep beneath the outer layer of tissue in the armpit and feels different from fat beneath the skin.
For a sentinel lymph node biopsy, a procedure where a doctor examines the lymph nodes, they divide the layer of tissue, known as the fascia, beneath the skin. Deeper to the large chest muscle (the pectoralis major muscle) is the clavipectoral fascia, a sheet of tissue covering and protecting large blood vessels and nerves in the armpit. Two important large blood vessels, the lateral thoracic artery and the thoracodorsal artery, can be found during surgery in this area.
There are also two main nerves a surgeon needs to be careful of during this type of operation: the long thoracic nerve and the thoracodorsal nerve. If the long thoracic nerve is injured, the serratus anterior muscle (a muscle located on the side of the chest) can stop working properly, which causes the shoulder blade to stick out unusually. It can be compared to a wing being extended out and hence this condition is referred to as ‘winging of the scapula’.
There are also several smaller nerves that go through the fatty tissue of the armpit, including the intercostobrachial nerve. Injury to these smaller nerves can result in a numb feeling in the upper part of the arm on the inside. The surgeon must be careful not to come close to a nerve bundle called the brachial plexus while operating in the armpit area, as long as they stay beneath a large vein, known as the axillary vein. This vein acts as a landmark for the surgeon. Going above this vein could cause severe swelling due to lymph fluid build up (lymphedema) and nerve damage, it also doesn’t help get more lymph nodes for the procedure.
Why do People Need Axillary Sentinel Lymph Node Biopsy
A sentinel lymph node biopsy is a medical procedure often used to check for the spread of cancer, especially for simple types of breast cancer like ductal and lobular carcinomas. These types of cancer can spread to the lymph nodes, which are small organs that produce and store cells that fight infection and disease. This biopsy helps doctors to stage your cancer, telling them how advanced it is and helping to choose the most effective treatment.
However, this procedure isn’t used for all cases of breast cancer. For example, sarcomatous tumors – a type of tumor that behaves like a malignant soft tissue tumor – typically spread to the lung and do not involve the lymph nodes in the armpits (axillary lymph nodes). As such, these types of tumors, like the cystosarcoma phyllodes tumor, aren’t typically evaluated with a sentinel lymph node biopsy.
Before the biopsy procedure, doctors often use imaging tests like ultrasounds, mammograms, or MRIs, to look for signs of possible lymph node enlargement. If these imaging tests suggest that the lymph nodes are larger than normal, a core needle biopsy is usually performed before any lymph node surgery. If the biopsy shows that cancer is present, a complete removal of the axillary lymph nodes may be necessary. This decision usually depends on the doctor’s assessment.
It’s important to note that some patients who are about to receive chemotherapy may undergo lymph node sampling before starting their treatment. This is because sentinel lymph node biopsies performed after chemotherapy may not provide reliable results.
Whether to perform a sentinel lymph node biopsy during prophylactic mastectomy, which is a surgery to remove one or both breasts to reduce the risk of developing breast cancer, is a topic of ongoing debate. However, because hidden cancer is found in 7% to 10% of removed breast tissue during prophylactic mastectomies, many clinicians will offer a sentinel lymph node biopsy to high-risk patients.
Lastly, the sentinel lymph node biopsy has been shown to be effective in patients with multicentric breast cancer, meaning that there are two or more tumors, all of which have started from different places within the breast. It’s a helpful tool for determining the need for the removal of lymph nodes, particularly among those who have no clinical signs of having cancerous lymph nodes.
When a Person Should Avoid Axillary Sentinel Lymph Node Biopsy
Sometimes a procedure called a sentinel node biopsy isn’t recommended for people who have a large amount of disease in the armpit area or large breast tumors. This is because it’s likely these patients have a lot of disease in their lymph nodes. However, some studies show that it might be beneficial to do a lymph node biopsy (a test to check for disease) before surgery. If this test comes back positive, it means that the patient is more likely to need additional surgery to remove more lymph nodes due to more disease spread.
Whether to use a sentinel lymph node biopsy in patients getting a specific type of chemotherapy before surgery isn’t quite clear. This is because, after this type of treatment, the biopsy might not accurately reveal whether the lymph nodes are affected, and may miss signs of the disease over 10% of the time. Therefore, most people will have a lymph node biopsy before they start this type of chemotherapy.
Equipment used for Axillary Sentinel Lymph Node Biopsy
To carry out this operation, a surgery room is needed with all necessary surgical tools, some assisting hospital staff, and anesthesia to make you feel no pain during the procedure. For an ‘axillary sentinel lymph node biopsy’ that is, a procedure used to check if there’s cancer in your lymph nodes near the underarm area, a handheld gadget called a gamma probe is also required if using what we call a radiotracer. The radiotracer is injected into your body, which then collects in any cancer cells and can be detected by the gamma probe.
There are various types of this gamma probe tool available. The usual ones will give a reading of the radioactive count and average radiation levels. The lymph node we examine is radioactive after this type of biopsy, therefore, how doctors handle any leftover radiation in the surgery room is done according to the rules of the hospital.
Who is needed to perform Axillary Sentinel Lymph Node Biopsy?
Surgeons who specialize in general, cancer, and breast surgery, are trained to perform a special procedure called a ‘sentinel lymph node biopsy’ for people with breast cancer. This procedure is usually done under general anesthesia or deep sedation, which means you’ll be asleep or deeply relaxed.
If they’re using something called a ‘radiotracer’, a special type of doctor known as a radiologist will place it either in or next to the area where the tumor is, or in the tissue just under the nipple. The radiotracer is used to help doctors see the affected lymph nodes more clearly. This all takes place before the procedure itself.
Preparing for Axillary Sentinel Lymph Node Biopsy
Before undergoing surgery, it’s essential that patients understand why the procedure is necessary. This is known as informed consent. In medical terms, ‘completion axillary dissection’ refers to surgically removing lymph nodes from the armpit area. This is typically not done at the same time as a sentinel node biopsy (a test to check if cancer has spread to the lymph nodes). However, in special cases where immediate test results are available during the surgery, the surgeon might carry out completion dissection immediately.
On the day of surgery, if a radioactive substance is going to be used to track lymph nodes, the patient needs to be booked in for an injection early in the day. This high-tech procedure, known as lymphoscintigraphy, is usually optional. It can be helpful if the surgeon is unsure if a key lymph node (referred as sentinel node) might be located elsewhere, like near the chest bone.
However, it’s worth noting that the nodes around the chest bone, known as internal mammary nodes, aren’t actually removed during the surgery. It’s important to know because cancer can often spread to these nodes, particularly in tumors located in the lower inner area of the breast.
How is Axillary Sentinel Lymph Node Biopsy performed
Preparations for surgery are made in the usual manner. Taking a sample of the axillary, or underarm, lymph node is done before any planned breast surgery on the same day. If blue dye is being used along with a radiotracker (a tool to track the movement of substances within the body), it is injected either near the tumor without using any imaging to guide it or under the area of the nipple. The injection is done just as the procedure is about to start. The rationale behind this is that blue dye molecules are smaller than the radiotracker and move more quickly in the lymphatic system, which is part of your immune system. Massaging the breast helps the blue dye to move more effectively. If the radiotracker has been injected beforehand, a tool called a gamma probe can be used to figure out where to make the cut, which is usually to the side of the large chest muscle.
The gamma probe then helps guide the surgeon through the fat under the skin and into the fatty pad in the armpit towards the lymph node that shows up on the probe’s detector. If blue dye is being used, that lymph node is usually also blue. Surgeons need to be careful not to point the gamma probe towards the injection site on the breast, as it can give a false reading of the level of radioactivity, leading to a misguided removal procedure. Once the lymph node is identified and removed, a reading is taken off of the field, and then another reading is taken within the wound. If the reading within the wound is high, the search for an additional lymph node may continue. After making sure there is no bleeding, the wound is closed, based on the surgeon’s preference. A quick analysis of the lymph node during the surgery is not needed if complete removal of the armpit lymph nodes is not planned based on the results.
If only blue dye is being used, the cut is made at the side edge of the big chest muscle. The blue-dyed node can usually be located by just visually looking for it.
Possible Complications of Axillary Sentinel Lymph Node Biopsy
A sentinel lymph node biopsy is a more minor operation compared to a full axillary dissection (surgery to remove underarm lymph nodes). However, like any surgery, it comes with its own risks. These could include bleeding, infection, nerve damage, lymphedema (swelling caused by a blockage in the lymphatic system), and the chance that more surgery might be needed if there are a lot of affected nodes or if the disease returns to the underarm area. Despite these potential risks, this biopsy is generally seen as a low-risk procedure.
What Else Should I Know About Axillary Sentinel Lymph Node Biopsy?
In the treatment of breast cancer, a technique called sentinel node biopsy has significantly improved patient care. It has saved countless women from the complications related to a more invasive procedure known as axillary dissection.
In 2010, a key study by the reputable research group ACOSOG showed that sentinel node biopsy provided excellent control of cancer within the region and did not lead to a decline in survival rate among early-stage breast cancer patients. This study compared patients with small to medium-sized tumors (Technical terms: T1 and T2 lesions) who received either sentinel node biopsy or complete axillary dissection, followed by chemotherapy.
Even though this study had some limitations, its findings have been widely accepted in the medical community. As a result, the more invasive axillary dissection surgery is no longer a commonly chosen treatment for patients with positive sentinel nodes.
Further research confirms these findings, showing that choosing sentinel lymph node biopsy over axillary lymph node dissection does not impact the overall 10-year survival rate in these breast cancer patients.
