Associate Professor Rod Dunbar (University of Auckland) explains the procedure of lymphoscintigraphy as a technique to determine the first lymph nodes melanoma will spread to.
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Dr Roger Uren
DR ROD DUNBAR
In melanoma, it is important to find out which lymph nodes would be the first ones that the melanoma cells would go to. And one very easy way to do this is to inject a substance in the same place as the melanoma and to track where that substance drains and to find the first lymph node that that substance accumulates in. And what they do is they mix up a dye and a radioactive tracer – and when they inject this into the skin, the radioactive tracer can be shown up using a technique called lymphoscintigraphy, and lymphoscintigraphy is a fancy way of saying, basically, we look for the shininess of the radioactivity using a particular kind of camera. And they can actually watch as the dye moves through the lymphatic tubes, and you can actually see it following a path, and then it ends up – bing – in a lymph node, which becomes very brightly stained in quite rapid time, it only takes 10 or 15 minutes for this to happen. Once that has happened, they can identify the lymph node which is the first lymph node that the melanoma cells would have gone to, and obviously, if that is the first lymph node that the melanoma cells would have gone to, if you then go in surgery and take that lymph node out, then you would be able to tell if the melanoma has spread, and so that’s what they do. And the way that they find that that melanoma is the right one is, of course, the dye also had a blue colour to it, and so they go in through the body and have a look for the lymph node that was blue in that particular area. Then they pull that lymph node out and the pathologists have a look at it, and then they slice it up in many different ways, and they go looking for the presence of melanoma cells, and if there are not melanoma cells there, they say you are probably okay, you are probably clear, we don't need to do anything else. But if they find melanoma cells, then what they will generally do is they will go in with further surgery and clear out a lot of the lymph nodes in that region to try and remove any potential melanoma that may have spread.