Sentinel lymph node

The sentinel lymph node is the hypothetical first lymph nodereached by metastasizingcancercellsfrom 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 lymphis unidirectional.

Uses

The concept of the sentinal lymph node is important because of the advent of the sentinel lymph node biopsy technique, also known as the sentinel node procedure. This technique is used in the stagingof 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.

To perform a sentinel lymph node biopsy, the physician first injects blue dyeand a harmless radioactive substancenear the tumor. This is usually done several hours before the actual biopsy. Then, during the biopsy, the physician visually inspects the lymph nodes for staining and uses a Geiger counterto assess which lymph nodes have taken up the radionuclide. One or several nodes may take up the dye and radioactive tracer, and these nodes are designated the sentinel lymph nodes. The physician then removes these lymph nodes and sends them to a pathologistfor rapid examination under a microscopeto look for the presence of cancer. A frozen section procedureis commonly employed (which lasts 20-30 minutes), so if tumor is detected in the lymph node a further lymph node dissectionmay be performed.

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. The main uses are in breast cancerand malignant melanomasurgery, although it has been used in other tumor types with a degree of success (Tanis et al 2001a).

The sentinel node procedure in breast cancer was pioneered at the John Wayne Cancer Institutein the 1990s, and confirmative trials followed soon after (Tanis et al 2001b).

References

• 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.
• 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.

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It uses material from the http://en.wikipedia.org/wiki/Sentinel+lymph+node Wikipedia article Sentinel lymph node.