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You may have heard people talk about lymph nodes when discussing a cancer diagnosis. Your next thought may have been, “What in the world are lymph nodes?”

You might be trying to search through your memories from science class. You may have a vague idea or even have felt a swollen lymph node, if you had a sore throat or a lot of sinus drainage. Still, the exact way to describe what lymph nodes are and their function eludes many.

Lymph nodes are small lima bean-shaped structures, generally less than a centimeter in size. They are simply a cluster of cells covered in a capsule of connective tissue. Lymph nodes are an important part of our immune system. In fact, they play a vital role in our body ‘s ability to fight off infection.

One of their jobs is to function as filter. The goal is to trap viruses, bacteria, and any other cause of illness before it gets out into the other parts of the body. Imagine them as your protective gatekeepers. We are trying to keep the infection or whatever the problem is contained to one area and not let it get into other systems or other areas of the body.

I mentioned lymph nodes are made up of a cluster of cells, specifically, lymphocytes and macrophages. (Wait! There is no reason to glaze over. I promise not to ambush you with piles of medical jargon.) Those are simply types of white blood cells. White blood cells are better known as our army of infection fighters. Like most armies, it is made up of different types of soldiers who all have their own job.

Lymphocytes (part of the cluster of cells that make up lymph nodes) capture the invaders. Their job is to find, recognize and capture the bad guy that does not belong. Whether it is an infection, a foreign object or foreign body (like a splinter), or an invader (like cancer cells).

Then the macrophages spring into action. I always think of these cells like the “Pac-Man” cells. Their job is to break down any toxins, those invaders, or infection, whatever it is that does not belong there. Macrophages are going to break it down and get rid of it.

Lymph nodes also filter something called the lymphatic fluid which circulates through our body. It is kind of like a highway system. A highway system made up of lymph nodes, lymph vessels, and the lymphatic fluid. It helps us get rid of toxins and move those white blood cells to wherever they need to go, wherever there is a problem in the body. Whether it is an injury, a bug bite, an infection, a cut or maybe even cancer cells, we send our army to take care of it.

Our lymph nodes, lymph vessels, and lymphatic fluid make up our lymphatic system, which is part of our circulatory system. Most commonly, we think about blood circulating through blood vessels with any mention of our circulatory system. Did you know we have a second highway system circulating lymphatic fluid filled with infection (aka “bad guy”) fighters and we are filtering it through lymph nodes all through our body? We do. Isn’t it amazing? No matter where a bad guy shows up in our body, we will send our army through the lymphatic fluid and use our lymph nodes to fight.

Lymph nodes are typically located in groups. Each group of nodes are responsible for filtering or draining a specific area in the body. These groups of lymph nodes can be found all through our body, such as under the chin, in the neck, above your collar bone, down the middle of your chest, in your armpit, your groin, your abdomen and elsewhere. Ever have a sore throat or a lot of sinus drainage? You may have felt a swollen little pea-sized knot under your jaw in your neck. That’s right…a lymph node (filled with infection fighters) at your service .

Lymphatic System

Can you picture your highway system inside, yet? Hundreds of lymph nodes throughout your body allowing white blood cells and lymphatic fluid to travel and circulate to wherever they need to go. Now imagine if a cancer cell sneaks its way into a lymph node, into one of our gatekeepers. The cancer cell has access to the highway system and can travel throughout the body as well, which is exactly what we do not want to happen.

Knowing this, it makes sense why it is so important to determine if any cancer cells are found in the lymph nodes when a patient is first diagnosed. In a previous post, we discussed the staging of cancer, particularly the TNM system used for solid tumors. The “N” refers to lymph nodes. Are any lymph nodes involved (positive for cancer)? If so, how many lymph nodes have cancer cells in them?

When undergoing work-up, a patient will typically have a biopsy of the mass or area of concern. Sometimes a swollen lymph node may be the first sign of concern and we will directly biopsy the node. If a patient has surgery to remove a mass, the surgeon may also remove the nearby lymph nodes for evaluation. If any cancer cells are found, we call it a “positive” lymph node.

Once we know cancer cells have gotten through one of our gatekeepers (a positive lymph node), the question becomes, “How far down the highway did it get?” We may need to go back and do additional surgery to remove more lymph nodes to see how many are involved. Then the next obvious question is prompted.

If the cancer cells got through the gatekeeper (lymph node) and down the highway system, did they get off on any of the ramps? Did the cancer cells stop off in the liver? Did they get off the ramp and head to the lungs? Did they go to the bones? Often, your oncologist will order scans to confirm there are no other areas of concern.

Our lymph nodes and lymphatic system are one of the main ways cancer can travel and metastasize, moving from where it started to somewhere else in the body. Determining whether lymph nodes are involved at the time of diagnosis provides a critical piece of information, drives treatment recommendations, as well as patients’ treatment decisions.