Back To CoursePathophysiology Textbook
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When we travel to our most favorite destinations, be it Aruba, Jamaica, Bermuda, or the Bahamas, as long as there's a beach, we'll probably be happy. How we get there is another story. We may have to drive along a road from our home to the airport or seaport and from there travel via specialized air channels or sea lanes to get to where we want to go. Along our journey, we face the dangers of crashes and other things. This analogy is similar to how some very bad cells may spread around your body.
I wouldn't be surprised, whether from another lesson or from your own education, if you've heard of the very important term metastasis, which is the spread of cancer cells around the body. Everyone uses this term left and right, but few people can explain how it begins or why it may occur. Frankly, even scientists don't fully understand the answers to those questions, but at minimum, I'll tell you about the fundamental answers to these questions.
First of all, a cell doesn't become cancerous over nothing. No! There's a reason. There's a whole sequence of events of a normal and healthy cell becoming cancerous. Actually, it's usually quite difficult for a normal cell to become malignant, let alone survive for long.
The details of why this occurs were discussed in the lesson that went over the initiation, promotion, and progression of cancer. In summary, these steps cause a cell to mutate, then multiply, and finally invade surrounding tissues and spread around the body, respectively. In order for this spread to occur something important must happen first.
You see, a collection of cancerous cells, known together as a malignant tumor, can only grow so large at first. That's because when you grow bigger and bigger as you go from infant to toddler to teen and beyond, you need an increasing amount of nutrients to do so. That's why people who grow up in very poor or war-torn conditions are often small in stature; it's because they didn't get enough nutrients while growing up.
Similarly, if a tumor wants to grow bigger and start spreading around, it needs more and more nutrients as it grows. To get these critical nutrients, it must establish a connection to one thing that carries these vital nutrients around your body. It's called the vasculature, or your blood vessels. Just like parasites that like to leech off of your blood for nutrition, so, too, do tumors leech off of your life-giving force to eventually kill you.
The process by which new blood vessels form or sprout from existing ones in order to connect to the tumor is called angiogenesis, or tumor angiogenesis in our specific cause for new blood vessel formation. The tumor secretes all sorts of chemicals, including VEGF, or vascular endothelial growth factor, that tell the body to start growing branches and tentacles off of existing blood vessels directly to the tumor. Once this connection is established, the tumor can grow like crazy.
Just as an interesting side-note, a tumor can grow so fast and large thereafter that it may actually outgrow and outstrip its own blood supply. If this happens, the tumor cells obviously begin to die, leading to the formation of very soft, fluid, and often pus-filled necrotic areas sometimes found in late stages of certain cancers.
But, I digress. After the new connection to your body's vasculature is established, the cancer cells use the mutations they underwent during their development to their advantage. These mutations allow a cancer cell to basically unstick itself from its surrounding area, something normal cells cannot do, and begin to move towards the blood vessels or lymphatic vessels and force these vessel walls open - and therefore gain entry into your vasculature.
Once inside of your blood vessels, the cancer cells aren't home free. These blood vessels are like the roads or sea lanes you use to travel to your destination. Before you can get to your destination, you must endure slick roads, other cars trying to run you off the road, icebergs (okay, maybe not in the Caribbean) - you get the point.
Similarly speaking, most cancer cells that enter the blood vessels die. Most cancer cells do not complete their journey to their vacation spot. This occurs for many reasons, including the fact that some of them:
A very small amount of cancer cells will complete their journey to their destination. Where they go exactly depends on many factors, including specific receptors on the cancer cells themselves and on the tissues and organs they may be targeting. Common places cancer cells love to spread include the lungs and liver.
Once they spread around the body, it becomes much more difficult to treat these cancer cells. For example, surgery alone will not be curative of metastatic cancer. You'd need to use chemotherapeutic drugs and even radiation therapy in some cases.
One other interesting thing is that in very rare cases, cancer can be spread iatrogenically - that is to say, due to a medical procedure. One example of this is if a needle is used to try and extract a sample of a malignant tumor for analysis, the cancer cells can latch onto the needle and be dragged out, or seeded, through the incision site. Again, it's a rare occurrence, but it's possible.
So, now you know how cancer spreads around the body and also how it is actually difficult to do so. Remember some key terms from this lesson:
'Metastasis' refers to the spread of cancer cells around the body. In order for this to occur, it's very important for cancer cells to start the process of angiogenesis, or the process by which new blood vessels form. They do so by secreting chemicals such as VEGF, or vascular endothelial growth factor, in order to 'entice' the blood vessels to grow branches towards the tumor site.
Once angiogenesis occurs, the cancerous cells can invade blood vessels or lymphatic vasculature. The cancer cells can then spread around the body, notably to the lungs and/or liver among many other places specific to different types of cancer.
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Back To CoursePathophysiology Textbook
20 chapters | 274 lessons