Eli5: How does cancer actually kill people?

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Like, I get the cancers that attack vital organs, like lung cancer, but, how exactly does, for example, skin or breast cancer?

In: Biology
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At some point most cancers spread if you live long enough, so cancer in the breast will eventually find its way through he bloodstream to another organ and take up residence.

There are a number of ways it can do so, but I will list the top 3

1. Interferes with the function of a major organ. The organ needs to do stuff to keep the body alive, having a giant mass in the organ makes that job more difficult like way more difficult.

2. Takes energy from the organ. Cancer is a hungry hungry mass, it uses way more energy than the surrounding tissue and causes the surrounding cells to die from hunger.

3. Interferes with blood and transport of necessary stuff. The cancer can block major arteries and veins and make blood flow stop. Lack of blood will kill the organ.

Cancerous cells originating in non-vital organs can travel around the body via the circulatory or lymphatic systems. They can then land in vital organs, like the lungs or the brain, and start growing new tumors there. This is called metastasis.

It is possible to have a benign tumor in a non-vital organ which is incapable of metastasizing. These can even grow very large without being life-threatening.

It replaces the good little workers in your body with workers that don’t work at all, or worse do their job incorrectly and spread themselves around that organ, and eventually your body instead. This makes the good workers have to work harder and harder to get less done until the work just stops being done all together. That’s when you die.

TLNGR:
people typically die from complications brought on by cancer. it interferes with proper functioning of a system/organ, shuts it down and leads to death. I guess that’s how anything kills us tho?

Most processes by the body are highly regulated, especially the process of cell division. It takes energy and may things can go wrong. Cancer is unregulated cell division, the cancer is multiplying on its own.

This takes up resources and energy, and cell-signaling molecules being are released. This which can affect different tissues and organs nearby, or cause chronic inflammation, which leads to complications

The immune system can come in to kill this cancer cell, some white blood cells can smell out those messenger chemicals and use them to find the cancerous cell so it can devour it. Most times it works, but there can be complications.

These reproduced cancer cells have the same identifying components as the rest of the body, so the immune system must target itself to kill the cancer. The immune system has something like a memory, and attacking “the self” also gets out of control/unregulated. Now auto-immune complications are involved.

Cancer cells are growths that grow in random directions and take over or replace good cells that we need to survive. Cancer cell don’t do anything other than grow.

It may start as skin or breast cancer, but it spreads through your body, and that’s when cancer gets dangerous for real.

It can rupture blood vessels and cause haemmorhaging.

It can disrupt the function of the organs/structures it invades (eg. having a big lump in your lung makes breathing problematic…)

But one of the biggest effects is that it just floods you with cellular waste-products. You can end up with *pounds* of cancer in you, and the thing about cancer is that its metabolism is turned up to 11 all day errday, so all that tissue is *constantly* pissing in your bloodstream and just plain poisoning you faster than your liver and kidneys can keep up with.

Cancer doesn’t specifically kill a person on its own, instead it stops other organs from being able to function properly by basically getting in their way.

So a tumour growing in the brain for example will start putting pressure on the surrounding brain tissue and displacing it – without that brain tissue your brain won’t be able to function properly, and certain faculties will start to fail.

A tumour growing in the stomach or intestines may cause blockages and problems to those organs – block your intestine and you cannot eat, or the tumour could damage the intestine walls and cause bleeding and infection.

Lung cancer will cause tumours to grow in the lungs – blocking the passage of air and limiting the oxygen you can absorb.