Sentinel Node Biopsy in breast cancer staging.
A sentinel lymph node biopsy is a procedure that was developed to identify metastasis (spread of) breast cancer to the underarm lymph nodes (axillary lymph nodes).
However, this biopsy means that doctors can check the lymph nodes without having to do a traditional axillary lymph node dissection.
By way of background, the lymph ducts of the breast firstly drain the lymphatic fluid to one lymph node. Next, the lymphatic fluid drains through the rest of the lymph nodes underneath the arm.
NOTE: The Lymph nodes are the ‘N’ categories in TNM breast cancer staging. However, in January 2018 The American Joint Committee on Cancer (AJCC) updated their 8th Edition of the staging classifications for breast tumors.
You can find a summary of the main changes, including amendments to the TNM categories, for staging breast cancer by clicking HERE. We will also be fully updating our staging articles on this site to include all the new information.
What does Sentinel mean?
Sentinel refers to an age-old military practice of posting a guard far away from the home-base. The guard is a lookout for early detection of an approaching enemy.
Here is a sentinel tower that gives some protection to the poor soldier.
Similarly, the first lymph node to encounter cancer cells (the approaching enemy), is the sentinel lymph node.
In a sentinel node biopsy, surgeons remove only this initial lymph node, the sentinel lymph node. Radiographers identify the sentinel lymph node with a dye. This dye is either a weak radioactive dye (technetium-labelled sulfur colloid) or a blue dye (isosulfan blue) that stains the lymph tissue a bright blue color.
This page is still fantastic for research. However, we have a new page with more up-to-date information on sentinel lymph node biopsies. Check it out!
Negative Sentinel Node biopsy usually means all axillary lymph nodes in the breast are cancer free.
The main advantage of the sentinel node biopsy is that a negative result will, in most cases, spare the breast cancer patient the ordeal of axillary node biopsies and dissections.
In fact, the SLN biopsy is so accurate the current debate is whether or not axillary dissections are necessary at all.
A ‘positive’ sentinel node biopsy finding, means that malignant cells are present in the sentinel lymph node. Sometimes, the sentinel lymph is mysteriously absent.
Positive sentinel nodes would warrant an immediate follow-up with a thorough axillary node assessment. But, sentinel lymph node biopsies, when negative, indicate that the axillary nodes are cancer free. So, medics consider a negative sentinel node biopsy result to be about 95% accurate.
However, a negative sentinel node result can cause a great deal of anxiety. This is because there may be discussion and consultation between the breast cancer patient and the treatment team as to whether or not the sentinel lymph node biopsy is ‘good enough’.
At which cancer stage is a Sentinel Node Biopsy necessary?
Treating doctors will use the sentinel node biopsy fairly early on in the treatment of breast tumors. Indeed, the sentinel lymph node biopsy is a part of the staging procedure.
A core biopsy showing an infiltrating lesion, especially when a physical examination of the axilla is negative, indicates a sentinel lymph node biopsy.
How ‘serious’ does a lesion or tumor have to be before getting an SLNB?
If the attending physician feels that a breast cancer is at an invasive stage they will request a sentinel node biopsy.
Another reason for a physician to request a SLNB is when a non-infiltrating lesion has characteristics suggestive of aggressive cancer.
This determination could be due to a variety of variables. These variable include high-risk factors and histological findings.
However, one of the most likely reasons to proceed is that the tumor is medium to large in size.
Sentinel lymph node biopsies are usually taken when the TNM classification is T1-2 N0 (tumor size 2-5 cm), but not for T3.
At TNM T3, the size of the tumor is greater than 5 cm and there is a very high probability of lymphatic involvement.
The adverse relationship between tumor size and nodal metastasis is quite consistent, but not a certainty. The correspondence rate varies between 67% and 100% .
This suggest that sentinel lymph node findings are less trustworthy in ruling out axillary metastasis as the size of the primary tumor increases.
On the other hand, other studies suggest that patients can avoid an axillary dissection in a third of cases if a sentinel node biopsy is performed first . This holds true, even with large T2 and T3 tumors.
What about ‘high risk’ DCIS?
The prevailing consensus is that a sentinel lymph node biopsy is unnecessary with DCIS.
Critics might argue that ‘high risk’ DCIS can potentially be ‘
There are two main reasons why breast cancer patients and researchers can be somewhat eager to have a sentinel node biopsy. Firstly, the sensitivity of the sentinel lymph node biopsy is a huge bonus. Secondly, the detection of the presence of ‘micro-metastasis’ on the lymph nodes.
However, it is important to remember that up to 90% of all ductal carcinomas can be treated and cured locally.
Lymph nodes in breast “micro-metastasis” of breast carcinoma
The term “micrometastasis” refers to extremely small amounts of malignant cancer cells. These very small deposits develop on the lymph nodes in breast or other secondary sites. However, they are so small they can only be seen ‘microscopically’.
It is somewhat of a ‘hot topic’ in cancer research at the moment. Advocates reason that through the use of specialized pathological techniques such as the ‘polymerase chain reaction’ method, malignant cells may be found on lymph nodes.
In the past, traditional methods, such as:-
- ultrasound
- CT scan
- PET
- MRI
can not detect this tiny micrometastasis.
So, the idea then is to perform a rigorous histological evaluation of the sentinel lymph node dissection. The specific aim of sentinel node biopsy is to search for micrometastases.
The hope is that if malignant cells are present, even in tiny quantities, aggressive treatments can begin right away. Obviously this early detection can lead to a huge improvement in prognosis.
Is a Sentinel Lymph Node Biopsy really Necessary?
Some studies estimate a five-year relapse rate for node-negative breast cancer patients to be around 30%. Proponents also claim that micro-metastases are present in 9% to 30% of negative lymph nodes upon re-examination.
So, this suggests that current histological detection methods may, the
However, it is a bit of a good news/bad news scenario. The potential for finding micro metastases creates a great deal of fear in women. Furthermore, some patients now doubt the authenticity and reassurance value of ‘image’ staging of the lymph nodes in breast, even when they are clear.
Those who specialize in SLN biopsies also point out that the sentinel node biopsy findings can be very sensitive. Indeed, they can sometimes spot a single malignant cell amongst one million normal cells. It is just as likely that the cell in question is just passing through the lymphatic system and is not an ominous indication. However, specialists may prescribe more surgery or chemotherapy.
Should some breast cancer patients NOT have the sentinel lymph node biopsy?
There are also other contraindications such as allergies or pregnancy. Another problem with sentinel node biopsy is at which point there is enough evidence of ‘clearly aggressive’ or metastatic disease.
The sentinel lymph node biopsy has so many positives that it is difficult to find a reason not to use it. There has been a fair bit of discussion as to whether or not factors such as prior breast surgeries, radiation therapy and chemical therapies compromise the results. The general consensus is no.
Sentinel lymph node breast biopsy not advisable for pregnant women
Most physicians will advise that
Allergies to the dye agents?
There will be a few breast cancer patients who have allergic reactions to either the
Before a sentinel node biopsy, women are often asked if they have any allergies to cosmetics, as there can be similarities.
Multicentric breast tumors contra-indicate the SLNB
A sentinel node biopsy is not appropriate for women with multiple (multicentric) breast tumors. This is because one cannot be sure which breast lesion has or has not metastasized to the sentinel lymph nodes in breast. The likelihood of a ‘false negative’ is therefore very high.
Radiation therapy of breast tumors also compromise the SLNB
It is quite common for oncologists to recommend radiation treatments to halt or slow cancer metastasis from the breast.
However, after radiation therapy, the lymphatic ducts and capillaries (lymph vessels) leak and then shrivel up. New pathways do eventually form but often in odd, jagged paths and not straight drainage paths anymore. So, at this point, the sentinel aspect is not reliable anymore.
Is a sentinel node biopsy appropriate after chemotherapy?
The short answer is yes. Indeed, around 40% to 48% of wom
In chemotherapy, the lymphatic ducts and capillaries around the breast tumor may undergo damage.
Again, this may affect the reliability of sentinel lymph node findings. In addition, chemotherapy often shrinks tumors leaving scar tissue and fibrosis that can make it hard for surgeons to inject a tracer or dye into the tumor.
There is no hard and fast rule in this regard. Lymphatic drainage patterns are generally in better shape following chemotherapy in comparison to radiation treatments. However, chemotherapy still damages the lymph drainage system.
Lymphatic flow continues through alternate routes and as time passes and the wound heals, restoration of the normal lymphatic channels occurs.
For this reason, it may well be advisable to map lymphatic drainage patterns prior to the sentinel node biopsy. However, if there is no evidence of subsequent infiltration at the primary sitem and a reasonable time period has passed since the treatment, there is little reason to doubt the accuracy of the sentinel lymph node biopsy.
The effects of previous breast dissections on sentinel lymph node sensitivity
A hot topic of debate among current breast cancer researchers is whether or not a prior lumpectomy or mastectomy can compromise the reliability of sentinel lymph node biopsies.
The traditional view is that previous breast surgeries might disrupt the lymphatic flow from the tumor site to the axilla. Thus, leading to higher ‘false negative’ results. However, this has not in fact been proven to be the case.
When lymphatic channels have been surgically compromised, flow continues through new and different routes. As damaged lymphatic channels gradually repair themselves, normal lymph drainage resumes. If the tumor occurs in an intact quadrant of the breast, even a recent reductive procedure, is unlikely to affect the reliability of the sentinel lymph node biopsy.
A prudent measure may be to combine the sentinel lymph node biopsy with pre-operative lymphoscintigraphy or other lymphatic mappings (LM) method. This is just to make sure the lymphatic flow is sound.
The sentinel node biopsy has been around since about 2001. So, there is enough experience now to assert that the effect of breast surgery itself on lymphatic flow is negligible.
Bear in mind that after all breast conserving therapies, the cancer will recur locally (along the breast or chest wall) 10% to 15% of the time. Furthermore, the cancer will metastasise to the lymph nodes in the breast, or other distant sites, at about the same rate. One can never really attribute metastasic disease specifically to ‘this or that’ procedure.
Can you trust SLNB after ‘local recurrence’ of breast cancer following surgery?
Lymph node assessment will be an ongoing part of breast cancer staging and treatment. The sentinel lymph node biopsy is typically something that occurs when you treat
Following breast surgery, a ‘local recurrence‘ means that the cancer has subsequently spread to somewhere on the chest wall of the breast. However, treatment and possible cure are still possible at this local stage.
Local recurrence of breast cancer would tend to rule out the use of SLNB, because the cancer is clearly aggressive and traditional axillary node biopsies would be a mandatory follow up.
Other evidence of axillary metastasis precludes SLNB
Sometimes a clinical evaluation indicates metastasis to the lymph nodes in breast cancer. Symptoms that indicate cancer has spread to the lymph nodes
- swollen lymph nodes or swollen glands in the axilla (under the arm)
- swollen neck lymph nodes.
In this case, the sentinel node biopsy is redundant. Excisional biopsies and possibly a ‘complete lymph node dissection’ (CLND) of level I and level II axillary nodes would be a likely course of action. (The ‘levels’ of axillary lymph nodes in breast refer to their anatomical location).
Specialists speculate that a senitary node biopsy could be a helpful prognostic indicator. This may hold ture even after confirmation of clinically positive axilla (NI) from fine-needle aspiration or core biopsy.
The problem with this notion is that the path of the dye or the radio-colloid agent may be blocked from tumor cells infiltrating the lymph vessels. This could prevent the identification of true sentinel nodes and produce false-positive results.
So you have a positive SLN, then what?
Sentinel lymph node biopsies are very accurate and reliable (around 90% to 95%) when they are negative for
Sometimes the biopsy results show a mix of negative (clear) and positive (cancerous) nodes. In this case the risk of spread to the axillary lymph nodes is still quite low, at around 10%. A CLND (Completion lymph node dissection) may not always be necessary.
Other factors that tend to suggest an increase in the probability of involvement of the other lymph nodes include the:-
- size of the lesion on the affected sentinel node
- size of the primary tumor
- presence or absence of lymphovascular invasion in the primary tumor
- amount of lymph node removal.
Reliability of other non-invasive methods in predicting breast cancer metastasis to axillary nodes
So, the axillary nodes are not yet clinically palpable on physical examination. Researchers estimate that either preoperative ultrasound imaging or a fine needle aspiration biopsy can determine the malignant status of the axillary nodes about 40 % of the time.
That is not a particularly high rate. So, in the absence of a sentinel node biopsy doctors will recommend routine follow-up scans at relatively short intervals.
Is it best to give women a choice regarding the SLNB?
Women undergoing breast cancer treatment may feelsome confusion regarding the choices they have regarding breast cancer treatment. Often, these choices revolve around the potential cancer-fighting benefits of a procedure versus the strain on the body and quality of life during and after.
However, the decision to reject axillary surgery and have a sentinel node biopsy instead is not necessarily the most prudent one. Even though the success rate is high and the side effects are minimal.
Some modern breast cancer treatment centers have access to clinical trials of the newest, best chemotherapy agents but those clinical trials often require the highest degree of staging.
Overall, the Sentinel lymph nodes in breast biopsy is a major ‘plus’ for breast cancer treatment.
Now that the SLNB is in widespread use, the challenge for researchers is to refine the groups of patients who will most benefit from the technique. The main benefit is in identifying patients with less aggressive cancers, who may not need complete lymph node dissection.
Additional benefits of bypassing axillary dissection, from a purely medical perspective, is that the normal flow of lymph fluid is relatively undisturbed. This adds to the benefit of preventative chemical and radiation therapies already underway.
For all breast cancers, between 70% to 80% of patients will not develop axillary lymph node metastasis. Therefore, for breast cancer patients undergoing multimodal therapies and with histologically negative sentinel lymph nodes, the rate of recurrent disease is extremely low.
Some cancer treatment centers, particularly those in less affluent parts of the world, have gone so far as to replace all other diagnostic measures for axillary metastasis with the sentinel lymph node biopsy.
It is reliable and accurate and improves long term quality of life by avoiding axillary dissection. This is, of course, somewhat of a radical conclusion but does highlight the practical and ethical dilemmas women sometimes encounter during breast cancer treatment.
The best advice is to develop good relationships with an experienced multidisciplinary breast cancer treatment team and to trust their judgement.
Here are a bunch of Q&A’s:
Why is sentinel lymph node biopsy done?
SLNB is useful for people with certain types of cancer in order to determine whether the cancer cells have migrated into the lymphatic system.
It is a routine test for individuals with breast cancer or melanoma. Sentinel lymph node biopsy is also useful in other types of cancer (to determine the sentinel lymph node closest to the cancer site). Other cancers whereby SLNB may be a useful test include:-
- colon cancer
- esophageal cancer
- head and neck cancer
- non-small cell lung cancer
- stomach cancer
- thyroid cancer.
It is important to distinguish between a primary cancer that has spread to the lymph nodes and an actual lymphatic cancer. The first, is whereby a breast cancer, for example spreads to the lymph nodes in the axilla region. The second is whereby the cancer starts in the lymph nodes themselves, for example, Non-Hodgkins Lymphoma and Hodgkins Lymphoma.
Symptoms in both case scenarios are an enlargement of the lymph nodes in the axilla or neck.
What are the risks of sentinel lymph node biopsy?
Some complications of sentinel node biopsy include
- bleeding
- pain or bruising at the biopsy site
- infection
- allergic reaction to the dye used for the procedure
- lymphedema (A condition in which your lymph vessels are unable to adequately drain lymph fluid from an area of your body, causing fluid build-up and swollen lymph nodes).
What is the risk of lymphedema?
The risk is very small.
How do you prepare for your doctor appointment?
Your doctor may ask you to avoid eating and drinking for a certain period of time before the procedure to avoid anaesthesia complications. Ask your doctor about your specific situation.
What does negative sentinel lymph node mean?
This means that cancer was not present in the nearest lymph node and the rest of the lymph nodes in the breast are left in place.
What does positive sentinel lymph node mean?
This means that cancer was present in the lymph node and additional lymph nodes in the area may need surgical removal.
What happens if a change or abnormality is found?
Results from a sentinel lymph node biopsy usually provide enough information for the doctor to decide whether or not surgery is necessary. Your doctor will also decide whether further tests or procedures are needed.
What are some potential side effects of sentinel lymph node biopsy?
Not everyone has side effects or experiences them in the same way. However, these include:-
- pain
- bruising
- arm numbness
- urine colored by the blue dye
- allergic reaction to the dye (rare)
- lymphedema.
Why is the involvement of the lymph nodes in the breast so important in breast cancer?
The lymphatic system is made up of connected lymphatic vessels (similar to blood vessels) that drain lymphatic fluid (clear plasma-like substance full of white blood cells) into lymph nodes in breast.
The lymph system is essential for removing any foreign organisms such as viral infection, bacterial infection and any invading, abnormal cells from the lymph fluid.
So, the lymphatic system is a vital part of our body’s immune system. There is a vast network of lymphatic nodes around our bodies.
However, because breast cancer often spreads to the underarm lymph glands first and then often to the neck lymph nodes, determining if these lymph nodes contain cancer cells is extremely important for assessing if the cancer is localised (contained within the breast tissue) or has spread.
Do swollen nodes under the arm indicate breast cancer?
No, not necessarily. If you find a lump in your armpit and you have no other symptoms it would be advisable to go for a mammogram as soon as possible.
However, there are many, many other reasons for lymph node swellings such as:-
- general or local infections
- reaction to drugs
- blocked glands from using deodorants.
- Infection (Often, but not always, painful lymph nodes that are soft and moveable indicate an infection.
It is always best to get any swollen lymph nodes or lumps checked out by your health care provider as soon as possible.
Further Reading
- Micrometastases to Lymph Nodes
- Lymphoscintigraphy and Breast Cancer
- Index of ALL our posts on Breast Cancer Screening
- Index of ALL our posts on Incidence and Survival Rates
- Core Biopsy
- Breast Cancer Staging: TNM and Lymph Node Involvement
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References
- Aasvold JN, Alazraki NP. (2005) Update on Detection of Sentinel Lymph Nodes in Patients With Breast Cancer. Seminars in Nuclear Medicine. 35: 116-128. 2005 https://www.ncbi.nlm.nih.gov/pubmed/15765374
- Filippakis G, Zografos G. (2007) Contraindications of sentinel lymph node biopsy: Are there any really? World Journal of surgical oncology 2007, 5:10. (January 2007) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1797176/
