Skin cancer requires an initial biopsy to discover whether the growth or tumor is indeed cancerous. Not all moles that appear as irregular or skin spots are cancerous. A biopsy provides your doctor with the information on whether it is necessary to proceed. It also may indicate whether the types of treatments need to be minor or major.
A very specific type of biopsy is called the sentinel node biopsy (SNB) or, more specifically, the sentinel lymph node biopsy. It serves a very specific purpose in determining the extent of the cancerous growth.
What are Lymph Nodes?
Lymph nodes (also called lymph glands) are part of the lymphatic system. They are shaped somewhat like a bean and appear as small bulges along this system. Lymph nodes exist for two major purposes. One is to intercept and remove any abnormal or foreign material coming from the lymph. The other is to generate an immune response.1
If any infection appears in the drainage region they govern, lymph nodes become enlarged. Yet, lymph nodes can also become infected. They can become the host of malignant or cancerous diseases.
What is the Sentinel Lymph Node?
The lymph nodes form groupings, clusters or even chains. The first node in this gathering of defenders is called the sentinel node. It is first-in-line to receive anything from the lymphatic system. Its importance for cancer treatment lies in the scientifically supported premise that any damage or defective lymphatic material must pass through it first.2
Sentinel (Lymph) Node Biopsy
The procedure known as sentinel node biopsy (SNB) or sentinel lymph node biopsy (SLNB) is among the latest techniques to determine how far skin cancer cells have spread. It was first used in 1992 by Morton for those cancer patients who suffered from cutaneous melanoma.3 SNB replaced other forms of more severe and invasive surgical intervention. These involved wide excision surgery to remove the tumor but leave the lymph nodes in place or further surgery that cut out all the lymph nodes, diseased or not, near the affected area. This latter surgery was called lymph node dissection or LND and was associated with significant complications after the surgery.
The purpose of the new method, sentinel lymph node biopsy was to decrease the amount of unnecessary removal of unaffected parts yet still remove all the cancerous sections.
Diagnosing and Preventing Cancer Spread using Sentinel Node Biopsy
This procedure is frequently used in cases of malignant melanoma.4 The procedure involves the skills of a surgeon as well as a pathologist. The process occurs under general anesthesia and may or may not be performed in a doctor’s office or small medical center.
The surgical procedure begins as follows. It involves blue dye and a radioactive tracer. The two processes act together to provide what is termed lymphatic mapping.
- The doctor injects a certain amount of radioactive material near the site of the tumor. This is called a tracer.
- Blue dye is also injected at the same area. This provides a distinct means of following the lymph system to the particular lymph nodes. In other words, the dye and tracer act to define the pathways and indicate the existence of one or more sentinel nodes
- With the help of a nuclear medicine scan, the surgeon follow the flow of the material through the system and perceive any indications whether any cancer cells are present and may spread. This will determine the next step.
- Removal of the sentinel or sentinel nodes for a biopsy.
- The malignant tumor is removed at the same time as the sentinel node. It, too is sent for a biopsy report and to even clarify what type of cancer is present5
Once the pathologist determines whether the sentinel node is cancerous (positive) or not (negative). The surgeon and your doctor will determine what the best steps to take next are. This includes surgery of different types. If positive, it may mean the removal of all associated lymph nodes in the area. It might also mean the removal of the particular lymph nodes closet and more vulnerable to the diseased sentinel node.
Benefits of a Sentinel Node Biopsy
Having a sentinel node biopsy does offer patients some advantages. This is particularly true when you consider the alternative approaches including LND. Some of the advantages relate to the use of this technology as an indicator of cancer. Other positive aspects of a SNB refer to benefits accrued by the patient.
- Accurate indicator of the spread of cancer. A positive sentinel lymph node indicates a high risk of cancer spreading to or already present in the other lymph nodes.
- A positive sentinel lymph node also indicates the high risk of the cancer reoccurring while a negative sentinel lymph node does not.
- By indicating the state of the sentinel node, SNB prevents unnecessary and extensive surgery such as removal of all the lymph nodes
- The procedure is beneficial for those who have melanoma. It is low-risk and is able to help medical staff identify those who may be at high-risk from cancer recurrence. As such, it helps reveal who and who should not receive more aggressive treatments including surgery6
The use of a sentinel lymph node biopsy to help treat and eliminate cancer is still in its infancy. Studies continue to be performed to record and analyze the effect of this method of treatment. To date, the results are more favorable than not. Overall, it has proven to be an effective tool in the ongoing battle against skin cancer.
1 Sarg, M. S. and Gross, A. D. (2007). “The Cancer Dictionary Third Edition”. New York: Checkmark Books.
2 American Cancer Society. (2011). “Skin Cancer”. Retrieved from www.cancer.org/Cancer/SkinCancer-Melanoma/DetailedGuide/melanoma-skin-cancer-diagnosed
3 Kanzler, M H., and Mraz-Gernhard, S. (2002). “Primary Cutaneous Malignant Melanoma and its Precursor Lesions: Diagnostic and Therapeutic Overview.” Retrieved from www.hudlaeknastodin.is/page67/assets/Primary%20cutaneous%20malignant%20melanoma%20.pdf
4 Memorial Sloan-Kettering Cancer Centre (2011). “Diagnosis and Treatment of Melanoma.” Retrieved from www.mskcc.org/mskcc/html/420.cfm
5 American Cancer Society. Op. cit.
6 National Cancer Institute (2011). “Sentinel Lymph Node Biopsy.” Retrieved from www.cancer.gov/cancertopics/factsheet/Therapy/sentinel-node-biopsy