Cancer is one of the most complicated illness that has ever existed.
Our bodies are made of tiny little building blocks called cells. All of the tissues in our body (including our blood, brain, eye) are made up of billions of these cells.
From the time of birth all of these cells follow a specific program that is encoded in them by their DNA. This includes programs about how big the cell should become, how many times it should divide (make identical copies of itself) and where it can travel to in the body.
Cancer occurs when one of these cells loses control and stops following the pre-set program. So it starts growing larger than usual and it starts dividing more often than it should and even travelling to other parts of the body it should not be allowed to go!
How does a cell lose control and become a cancer?
As mentioned previously each cell follows a program encoded in its DNA. Changes to the DNA for a variety of reasons cause the program to malfunction and the cell to lose control.
As an example let’s imagine that a 1mm spot of a bone is a parking lot for milk trucks (with calcium 😊) and each of these trucks make up a cell in that bone. But these are futuristic milk trucks (self-driving trucks that can make identical copies of themselves if needed) and inside each and everyone of these milk trucks is 30000 levers and each of these 30000 levers has 1000-10000 different settings! These levers and settings represent the milk truck’s DNA. Now imagine when each milk truck is created the levers are set in a specific way so that it can complete a certain role.
Every morning a few of these milk trucks are programmed to leave the parking lot, pick up the milk at the farm(s) and bring the milk to each house that requires milk and finally the milk trucks return back to their parking spots and park until the next day. Well in cancer something plays with the levers (DNA) in one of the milk trucks and now that truck starts to become bigger than the others, it starts to go on the wrong routes and park in places it should not and even starts to divide (create more of itself) in places it should not be even be to begin with! For example the= the milk truck may park and make more of itself in the brain (nervous system). When this happens this is called a metastasis. The brain is the site of metastasis but the milk truck (or bone cell) is the actual cancer.
What is even more crazy is that although the normal functioning milk truck can make an identical copy of itself (including the positions of the levers - when it is a healthy milk truck), when it is in a cancer state the milk truck produces different levers in different settings...so each of these milk trucks that arise from the cancer milk truck have different programs from one another and all of them behave inappropriately.
Why do these lever settings (DNA) change to begin with? This is a complex question that is still not fully understood. Some changes occur because of problems in the DNA itself that occur with aging, also exposure to carcinogens, such as tobacco, can cause levers to change and cause a cancer.