Rights: The University of Waikato Published 29 July 2008 Download

Associate Professor Rod Dunbar (University of Auckland) describes the lymphatic system and explains its role in the spread of melanoma.


Hayley's project relates to a system in the body called the lymphatic system, and the lymphatic system is the system that connects up your lymph glands. Lymph glands sound kind of complicated but you actually already know what they are because you know what happens when you get an infection. If you get a flu or a sore throat or something like that, quite often you get lumps developing in your neck or under your arms, and that is classically where the doctor will feel to see if there is an infection. Why should you get lumps under your arms or in your neck when you get an infection? Well, that is because there is a system which takes fluid and bugs from an area that is infected and concentrates it in a particular part of the body where it can meet immune cells, and that particular part of the body are called lymph glands, which we more properly refer to as lymph nodes.

The reason that happens is that your immune system has a very large number of very specialised cells which can fight infection, but the number of cells that can fight any one infection is very rare. So, for example, a number of cells that are capable of fighting the flu virus when it comes in is perhaps initially one in a million. So what you need to do is to concentrate a large number of cells in one area, and hoover up fluid that’s carrying the infectious particles and bring it to one area where those cells are concentrated so that the right cell can meet the bug and learn how to fight it. And there are various well known anatomical sites at which these collections called lymph nodes actually arise. But the anatomy of the fine tubes that drain into those lymph nodes is less clear, and these fine tubes are so fine that they’re very very hard to track. And what happens in melanoma patients, there is a possibility that the cells begin to spread through the body, and one of the ways is through these fine tubes called the lymphatic system. So the way it works is, just as if you have an infection in your skin, the lymphatic tubes are there to drag the bugs off to this little collection of white blood cells where they can fight the infection. The same tubes can be used by the melanoma to spread out of the skin. So one of the first signs that you are going to get very sick from the melanoma, potentially, is that the cells have moved from the skin, they have penetrated deep enough to access these fine lymphatic tubes and then they have swum their way – in fact, they’ve usually just been carried by fluid flow passively – down to the lymph nodes. And, unfortunately, lymph nodes is one place they can grow very nicely. So the other reason doctors need to examine lymph nodes and to feel for them is in patients with cancer, because one of the first signs that cancer has spread is that their lymph nodes swell, and in this case, it is not because the lymph nodes are fighting a bug, it is because the cancer is actually in there growing.

Medical illustration copyright © Nucleus Medical Art 2008