About cancer
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Cancer is not just one disease. There are over 100 different types of cancer, each with different names, effects and treatments. Even though each type of cancer is different, there are some basic things that are similar in most cancers.
To understand more about cancer, you first need to understand a bit about cells.
What are cells?
Cells are the building blocks of the body. They are very small and can only be seen under a microscope. There are billions of cells in an adult human body, but not every cell is the same. There are hundreds of different types of cells in the body and each has a different job. For example, bone cells are different from skin cells, which are different again from muscle cells. The cells work together to form organs such as the heart, brain or intestines.
Even though cells do different jobs in our body, they still have some things in common. Each cell has something called a nucleus. This contains DNA. The DNA contains genes, which are like instructions for our cells. Genes tell cells what to do and how and when to do it. Genes tell the cells when to reproduce (make copies of themselves). If a cell is damaged, instructions in the genes tell the cell how to repair itself or, if it is too damaged, that it is time for the cell to die.
How do cells reproduce?
Cells reproduce through a process called cell division. In cell division, the cell copies all its DNA and then divides into two identical cells. Normally, cells only reproduce to replace cells that have died or to make more cells when your body is growing. This way, your body carefully regulates how many cells are in your body.
Different types of cells reproduce at different rates. For example, cells in your mouth and the lining of your stomach and intestines live a short time and reproduce very often. Cells in your brain and spinal cord, called neurons, live a long time. In adults they almost never reproduce.
Cells and cancer
Cancer happens when there is a mutation, or change, in the DNA of a normal cell. The mutation causes the cell to act differently than a normal cell. Mutated cells do not die when they should. They reproduce even when the body does not need them to, usually much faster than normal cells. A cancerous cell is one that reproduces over and over again, forming two cells, then four, then eight, then 16, until it has made billions of copies of itself. Each of the copies has the same mutation.
This table explains some of the differences between cancerous cells and normal cells.
| Normal cells | Cancerous cells |
|---|---|
| Repair their DNA when it is damaged or mutated | Do not repair their DNA when it is damaged or mutated |
| Die when they are old or too damaged | Often do not die when they are old or damaged. Scientists call them "immortal." |
| Reproduce in a controlled way, only to replace dead or damaged cells or when you are growing. | Reproduce many, many times in an out-of-control way even when your body does not need them to. They can reproduce so much they crowd out healthy cells. |
| Mature to become a specific type of cell with a function in our body such as skin cells, muscle cells or blood cells. | Do not mature to have a function in our body. These cells are called immature. |
| Stay and grow where they are supposed to. | Invade (grow into) other areas of the body and cause damage. |
Cancer names
Most types of cancer get their name from the normal cell that the cancer comes from. For example, lung cancer is cancer that started from a mutation in a cell from the lungs. But many cancers in young people do not always start in a specific organ. They can happen anywhere in the body.
Cancer grade
As the mutated cells divide again and again to make more copies, more and more mutations happen. Remember, the cancerous cells do not die or repair themselves when they are damaged. Over time, the cancer cells look and act less and less like the normal cells around them.
- When cancer cells look very different from normal cells, we say the cancer has a higher grade.
- When the cancer cells look more similar to the normal cells, the cancer has a lower grade.
In general, a cancer with a higher grade is more likely to grow quickly, invade, and destroy cells around it and spread throughout the body than a cancer with a lower grade.
Most cancers in young people are high grade.
What is a tumour?
In some types of cancer, the mutated cells can grow into a mass or ball of cells. This mass of cells is called a tumour. Not all cancers form solid tumours. Leukemia is one type of cancer that does not form a solid mass – these cancer cells stay floating in the blood – a liquid cancer.
Tumours can be malignant or benign. Cancer cells in a malignant tumour can invade and destroy the cells around them and spread to other parts of the body. The cells in a benign tumor do not spread to other parts of the body.
How cancer spreads
The place the cancer first starts in the body is known as the primary cancer site. This group of cancer cells is called the primary cancer. Cancer cells can break away from the primary cancer and travel to other parts of the body through the blood or lymph. Lymph is a fluid that circulates through the body in little vessels, called lymph vessels. Lymph is an important part of our body’s immune system.
Sometimes these cells can get stuck in other tissues in the body such as the lungs or bone marrow. The cells then start to grow in this new place in the body. This group of cancerous cells is called metastasis (say: muh-TAS-tuh-sis).
Metastasis is still named after the place where the cancer first started, even though it is now in a different part of the body. For example, if bone cancer spreads to the lungs, the cancer cells in the lungs are still bone cancer cells.
In liquid cancers such as leukemia, the metastatic site is outside the bloodstream. For example, the leukemia may have metastasized (spread) to the fluid around the spinal cord or the tissue in the testes.
There are many types of cancer and each type is very different. For example, bone cancer is very different from leukemia. Each type of cancer has a different effect on the body and needs different type of treatment. Your health-care team will find out which type of cancer you have so that they can plan the right treatment.
Do all cancers need treatment?
As you now know, cancer is not just one disease. In fact, there are hundreds of different types of cancer and within each type of cancer there can be a lot of variety depending on:
- where the cancer is growing in the body
- how fast it is growing
- how different the cancer cells are from normal cells
- whether the cancer has spread to another part of the body
- how your body is responding to the cancer
Cancer is a life-threatening disease and so most cancers do require treatment. Often they need to be treated as fast as possible.
