Sentinel lymph node

The sentinel lymph node is the hypothetical first lymph node or group of nodes reached by metastasizing cancer cells from a tumor.

Physiology

The spread of some forms of cancer usually follows an orderly progression, spreading first to regional lymph nodes, then the next echelon of lymph nodes, and so on, since the flow of lymph is unidirectional.

Uses

The concept of the sentinel lymph node is important because of the advent of the sentinel lymph node biopsy technique, also known as a sentinel node procedure. This technique is used in the staging of certain types of cancer to see if they have spread to any lymph nodes, since lymph node metastasis is one of the most important prognostic signs.

may be performed. With malignant melanoma, many pathologists eschew frozen sections for more accurate "permanent" specimen preparation due to the increased instances of false-negative with melanocytic staining.

There are various advantages to the sentinel node procedure. First and foremost, it decreases unnecessary lymph node dissections where this is not necessary, thereby reducing the risk of lymphedema, a common complication of this procedure. Increased attention on the node(s) identified to most likely contain metastasis is also more likely to detect micro-metastasis and result in staging and treatment changes. The main uses are in breast cancer and malignant melanoma surgery, although it has been used in other tumor types (colon cancer) with a degree of success. [Tanis PJ, Boom RP, Koops HS, Faneyte IF, Peterse JL, Nieweg OE, Rutgers EJ, Tiebosch AT, Kroon BB (2001a). Frozen section investigation of the sentinel node in malignant melanoma and breast cancer. "Ann Surg Oncol" 8:222-6. PMID 11314938.]

However, the technique is not without drawbacks, particularly when used for melanoma patients. Failure to detect cancer cells in the sentinel node can lead to a false negative result - there may still be cancerous cells in the lymph node basin. In addition, there is no compelling evidence that patients who have a full lymph node dissection as a result of a positive sentinel lymph node result have improved survival compared to those who do not have a full dissection until later in their disease, when the lymph nodes can be felt by a physician. Such patients may be having an unnecessary full dissection, with the attendant risk of lymphedema. [Thomas J (2008). Prognostic false-positivity of the sentinel node in melanoma. "Nat Clin Pract Oncol." 5(1):18-23. PMID 18097453.]

The sentinel node procedure in breast cancer was pioneered by surgical oncologist, Armando Giuliano, MD at the John Wayne Cancer Institute in the 1990s, and confirmative trials followed soon after. [Tanis PJ, Nieweg OE, Valdes Olmos RA, Th Rutgers EJ, Kroon BB (2001b). History of sentinel node and validation of the technique. "Breast Cancer Res" 3:109-12. PMID 11250756.]

References


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