radioactivity greater than 3-4 times than the surrounding area.Surgeons typically use one of four criteria to identify sentinel nodes: Individual surgeon preferences dictate the number of lymph nodes that will be removed. After the sentinel node is removed, the surrounding area is checked for other nodes that are considered hot. This provides the surgeon the precise location of the sentinel node, preventing the extra tissue disturbance that goes along with the blue dye method. The gamma detector will indicate the area of the sentinel node when it shows an increase in count numbers nodes with high levels of radiation are called "hot nodes". After sufficient time has elapsed, a hand-held gamma ray detector is used to detect increased levels of gamma rays given off by the tracer. The radioactive tracer material (sulfur colloid) needs to be injected 4 to 6 hours before surgery for it to properly spread throughout the local lymphatic region. 2 3Īllergic reactions have occurred from the injection of the blue dye, but this is very rare (less than 2% of the time) and seldom severe. The marked node closest to the tumor is the sentinel lymph node. An angled incision is made in the armpit and the lymphatic vessel marked by the blue dye is located and traced until the lymph nodes are reached. The dye rapidly spreads throughout the region and within 5-10 minutes lymph nodes and vessels can be identified. The two methods are described in more detail below.Ī small amount of blue dye (often isosulfan blue or methylene blue) is injected into the functional elements of the breast (lobules, ducts, etc.). polled 410 surgeons in the American College of Surgeons and found that 90% use a combination method of blue dye and radioactive colloid. The methods are often used in combination, a recent survey by Lucci, et al. One method uses an injection of a blue dye and the other uses radioactive material and a gamma counter. There are two methods used to identify and remove the sentinel node and they differ in the way the sentinel node is located. The following sections on this page describe the process of SLN biopsy in detail: Watch a documentary on sentinel lymph node biopsy. If no cancer cells are found in the SLN it is much less likely that cancer cells have invaded the lymphatic system and moved to other parts of the body. The sentinel node is the first node to receive drainage from the tumor area, metastasizing cancer cells leaving the tumor are most likely to collect in the SLN. These are known as sentinel lymph nodes (SLN). If a cancer cell leaves the site from which it originated (the primary tumor) via the lymphatic system, it floats through the vessels until it reaches the next group of lymph nodes.įor any region of the body, it is possible to predict which lymph node(s) are most likely to have been reached by a migrating cancer cell. It includes an extensive network of vessels and some grape-like clusters of lymph nodes (regional collection centers). The lymphatic system is part of the immune system, the body's defense against infection. Migration of cancer cells to distant parts of the body often occurs via blood vessels (veins/arteries) and the lymphatic system. The rationale for sentinel lymph node biopsy is based on the idea that the spread of cancer is not a random event. One of the methods used to determine metastasis is sentinel lymph node biopsy, the removal of some lymph nodes. Fluorescent In Situ Hybridization (FISH)Īfter a lesion is diagnosed as cancerous, it is important to know if the cancer has spread to other areas of the body (metastasized).Computed Axial Tomography (CT or CAT Scan).
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