![]() There are various advantages to the sentinel node procedure. 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. The surgeon then removes these lymph nodes and sends them to a pathologist for rapid examination under a microscope to look for the presence of cancer.Ī frozen section procedure is commonly employed (which takes less than 20 minutes), so if neoplasia is detected in the lymph node a further lymph node dissection may be performed. One or several nodes may take up the dye and radioactive tracer, and these nodes are designated the sentinel lymph nodes. Then, during the biopsy, the physician visually inspects the lymph nodes for staining and uses a gamma probe or a Geiger counter to assess which lymph nodes have taken up the radionuclide. About 15 minutes before the biopsy the physician injects a blue dye in the same manner. This is usually done several hours before the actual biopsy. Scintigraphic imaging is usually started within 5 minutes of injection and the node appears from 5 min to 1 hour. A gentle massage of the injection sites spreads the sulphur colloid, relieving the pain and speeding up the lymph uptake. The sulphur colloid is slightly acidic and causes minor stinging. In the UK 20 megabecquerels of nanocolloid is recommended. The injection protocols differ by doctor but the most common is a 500 μCi dose divided among 5 tuberculin syringes with 1/2 inch, 24 gauge needles. The injected substance, filtered sulfur colloid, is tagged with the radionuclide technetium-99m. To perform a sentinel lymph node biopsy, the physician performs a lymphoscintigraphy, wherein a low-activity radioactive substance is injected near the tumor. In skilled hands and in a center with sound routines, one, two or three of the listed methods can be considered sufficient. In everyday clinical activity, entailing sentinel node detection and sentinel lymph node biopsy, it is not required to include all different techniques listed above.
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