What is Cancer?


Cancer is a collective name for many different diseases that can occur in different parts of the body. Cancer diseases have different symptoms, different prognoses, and are treated in different ways. They have one thing in common: They arise because one or more cells change and develop into cancer cells.

Cancer cells proliferate uncontrollably. Eventually, a cancerous tumor may have formed. The cancerous tumor may be in the way or otherwise, prevent the body from functioning properly.

There are also benign non-cancerous tumors. You can read about benign tumors here.

Cell division – a complicated process

Everything in the body is made up of many billions of cells. For example, the skin consists of skin cells and the liver of liver cells. The cells need to divide to form new cells. They replace old and damaged cells. In this way, the body can grow and function. Different cells divide often. For example, some blood-forming cells divide almost every day, while liver cells divide about once a month. Some cells, like nerve cells, can divide even more rarely.

When the cell divides, it first doubles its contents. Then the cell divides into two cells.

For the most part, cell division works as it should, but sometimes it can be wrong. There may have been damaged inside the cell so that it has changed. Changed cells that continue to divide can lead to cancer.

The genes control cell division

In each cell, there is a nucleus that contains the genetic mass, also called DNA. Parts of DNA are called genes. They control what the cell should do so that our body is built up and functioning. The genes also control cell division.

The cell division is carefully regulated. Some genes control when the cell divides. Other genes control when it’s time for the cell to stop dividing. There are also genes that control when the cell needs to repair the damage so that the damage is not passed on at the next cell division.

It can lead to cancer if there is an injury in precisely the genes that control the cell’s division or ability to repair an injury.

You can read more about DNA damage in the chapter Why cancer occurs.

From cell change to cancer

It is called cell changes when many cells in one area of ​​the body function differently due to DNA damage.

Many cell changes stop before they lead to cancer. But if the altered cells continue to divide, there is the risk of new damage in their DNA. For each new injury, the cells function more and more differently. Eventually, the cells have so much damages to the genes that they have become cancer cells.

Cancer cells have some typical characteristics:

  • They stop doing what they should.
  • They stop interacting with their surroundings.
  • They reproduce uncontrollably.
  • They do not die when they should give way to new cells.
  • They can grow into nearby tissues and after a while spread to other parts of the body.

Cancer cells usually form a nodule called a cancer tumor. There are cancerous diseases where cancerous tumors are not formed, such as leukemia. However, the leukemic cells cause damage by displacing other cells so that the blood cannot be formed properly.

It takes a long time for cancer to develop. It depends on where the body cancer begins. Some times it takes several years from the first DNA damage until the cancer is detected. Other times it goes faster.

Cancer develops in various stages

The development from normal cells to cancer is usually divided into a preliminary stage and four phases:

  • Precursor, hyperplasia.
  • The first phase, dysplasia.
  • The second phase, cancer in situ.
  • The third phase, invasive cancer.
  • The fourth stage, spread or metastatic cancer.

One phase does not have to pass on to the next phase. The changes can stop. This is especially true of the pre-stage and the first phase.

The precursor or hyperplasia cells become more numerous

In the pre-stage, the cells increase in number but behave as usual. It may be a precursor to cancer, but need not be. The body usually manages to deal with precursors or hyperplasia.

First phase or dysplasia – cell changes

In the first phase, the cells are multiple. They begin to change their appearance and lose their original function. Such cell changes can be seen with a microscope, for example, if you have left a cell sample from the cervix in a tissue sample from, for example, a birthmark. Cell changes can sometimes stop.

The second phase or cancer in situ – cancer that grows in a confined space

In the second phase, the cells are so changed that they have become cancer cells. In situ means in place and means that the cells are still growing in one place. They do not penetrate other tissues or organs.

The third stage of invasive cancer – cancer that penetrates into tissue all around

In the third phase, the cancer cells have changed even more. They move and penetrate organs and other body tissues that are all around.

The fourth phase or metastatic cancer – cancer that spreads to other parts of the body

In the fourth phase, the cancer cells enter the blood vessels and the lymphatic system and in this way spread to other parts of the body.

More about metastases

Cells that spread from a cancerous tumor to other parts of the body can form new cancerous tumors. They are called daughter tumors, or metastases. Metastases occur more frequently in some organs than in others, such as the lymph nodes, lungs, skeleton, liver, and brain. It is different for different cancers.

Tumor stage and tumor grades

If you are being treated for cancer you may read or hear different terms that describe the disease. One word that doctors often use to describe the spread of cancer is the tumor stage. The tumor stages are roughly in agreement with the different phases.

The word tumor grade is used to describe how the properties of altered cells are. For example, it can be how fast the cells grow and how different they have become.

This is how cancer develops

This is how cancer develops

As cancer develops, the cells change in different stages: one precursor and four stages. Here you can read more about them.

Why cancer occurs

Some cancers are hereditary and then it is safe to say what caused the disease. An example is the childhood cancer retinoblastoma.

But for the most part, it is impossible to say why an individual gets cancer. It is known that cancer begins with cell changes and that cell changes are due to a type of damage within the cell that makes the cell function more and more different for each cell division. But several things are important for a cancer disease to develop.

One thing could be how sensitive our cells are to the effects that can cause damage. Sensitivity varies from person to person.

Another thing is the age. The longer we live, the greater the risk that we will have different genes in the genes. Therefore, cancer is also more common as we get older, although children can also get cancer.

Various causes of DNA damage

DNA in a cell can be damaged for a variety of reasons. Here are some examples of what can cause such damage, also called mutations:

  • Environmental factors. Tobacco smoke, solar radiation, and pollution are some examples.
  • Some bacteria and viruses. The HPV virus is an example. The HPV virus is associated with, among other things, cervical cancer.
  • Chance. Cell division is a complicated process. Sometimes it gets wrong.

Some mutations are hereditary. Then you have received a damaged gene from a parent or from both parents.

The cell can usually repair DNA damage

It is quite common for DNA damage to occur in a cell. Many DNA damages you can live with without noticing anything. In addition, you have the vast majority of genes in a double set, one from each genetic parent. If a particular gene is damaged in a cell, it can sometimes suffice for the corresponding gene from the other genetic parent to function.

The cell can also stop the damage from being passed on if needed. Either the cell fixes the damage before the cell division or it destroys the cell itself.

Cancer can occur if the damage is in the genes that control cell division or the ability to repair or destroy itself.

How do I know if I have cancer? Can I prevent cancer?.

Treatment for cancer

How a cancer disease develops depends on the type of cancer involved. The disease also varies from person to person. But often the possibility of treatment is greater the earlier the disease is discovered. This is because the cancer cells have not been able to change as much as in later stages of the disease. It is the characteristics of the cancer cells that determine how easy or difficult it is to treat the disease. The size of the cancer tumor usually has less significance.

The more that is known about how the cancer cells behave, the more the treatment can be adapted to be as effective as possible, and with fewer side effects.

It is common with surgery, cytostatics or radiation to treat cancer. Sometimes there are other treatments as well. It is common for different treatments to be combined.

Cancer has always existed

Cancer has been around longer than humans. For example, dinosaurs have been found with cancer. Plants can also get cancer.

That’s why more and more people are getting cancer now

One reason why more and more people are getting cancer in our time is that we live so long. In the past, many people died of other diseases before they got cancer. The fact that more and more people are getting a cancer diagnosis is also because we have become better at finding and diagnosing cancer earlier, that is, separating cancer from other diseases.

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