Cancer cells

This page has information about cancer cells and how they are different from normal body cells. You can read about

Features of normal cells

Normal body cells have a number of important features. They can:

  • reproduce when and where they need to
  • stick together in the right place in the body
  • self destruct when they become damaged or too old
  • become specialised (mature). This means they have a specific role to perform for example as a muscle cell or red blood cell. 

Cancer cells are different to normal cells in various ways.

Cancer cells don't stop growing and dividing

Unlike normal cells, cancer cells don't stop growing and dividing when there are enough of them. So the cells keep doubling, forming a lump (tumour) that grows in size. 

A tumour forms, made up of billions of copies of the original cancerous cell.

Cancers of blood cells don't form tumours for example leukaemias. But they make many abnormal blood cells that build up in the blood.

Cancer cells ignore signals from other cells

Cells send chemical signals to each other all the time. Normal cells obey signals that tell them when they have reached their limit. They will cause damage if they grow any further. But something in cancer cells stops the normal signalling system from working. 

This 1 minute video shows how cancer cells send messages that tells other cells to grow and divide.

View a transcript of the video.

Cancer cells don't stick together

Cancer cells can lose the molecules on their surface that keep normal cells in the right place. So they can break away from their neighbours.

This helps to explain how cancer cells can spread to other parts of the body.

Read about how cancer can spread.

Cancer cells don't specialise

Unlike healthy cells, cancer cells don't carry on maturing or become so specialised. Cells mature so that they are able to carry out their function in the body. This process of maturing is called differentiation.

In cancer, the cells often reproduce very quickly and don't have a chance to mature. Because the cells aren't mature, they don't work properly. And because they divide quicker than usual, there's a higher chance that they will pick up more mistakes in their genes. This can make them even more immature so that they divide and grow even more quickly. 

Cancer cells don't repair themselves or die

Normal cells can repair themselves if their genes become damaged. This is known as DNA repair. Cells self destruct if the damage is too bad. Scientists call this process apoptosis. 

In cancer cells, the molecules that decide whether a cell should repair itself are faulty. For example, a protein called p53 usually checks if the cell can repair its genes, or if the cell should die. But many cancers have a faulty version of p53, so they don't repair themselves properly.

This leads to more problems. New gene faults or mutations can make cancer cells:

  • grow faster
  • spread to other parts of the body
  • resistant to treatment

Cancer cells can ignore the signals that tell them to self destruct. So they don't undergo apoptosis when they should. Scientists call this making cells immortal. 

Cancer cells look different

Under a microscope, cancer cells may look very different from normal cells. Cancer cells:

  • are different sizes and some may be larger than normal while others are smaller
  • often have an abnormal shape
  • often have a nucleus (control centre) that looks abnormal 

Find out about different types of cancer according to the cell type they start in 

Next review due: 6 October 2026

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