Can you catch cancer?

By Safiya Zaloum

There are some diseases that you can catch and some that you can’t. Something like the flu or a cold is contagious, meaning that you can catch it from someone else. These diseases are caused by viruses or bacteria that can be passed from one person to another. However this is not what causes cancer, so you cannot catch cancer from someone else.

What is cancer?

Cancer is an abnormal group of cells. It starts with a change in one cell or a small group of cells. These then divide rapidly out of control to produce more cancer cells. This begins when DNA is copied – inside each of your cells is a nucleus containing all of your DNA. Cells divide to form more cells but to do this, a cell must copy everything inside of itself to make 2 copies, including your DNA, before it splits into 2 cells.

When DNA in a cell is copied, the cell checks it carefully for mistakes. If there is a mistake in the DNA, this cell usually dies, however sometimes it ignores this instruction and divides anyway. Now there is a cell with damaged DNA. It no longer has the correct instructions that it normally would, so starts to divide quickly, often quicker than the cells around it forming a cancer.

When we think of cancer we usually think of a tumour – a lump. But not all cancers are solid tumours, you can have cancer of the blood where cancer cells build up in the blood but do not group together. There are many different types of cancer, each named from wherever it originated. Despite there being more than 200 different types of cancer, which require different treatments, there are some main characteristics of cancer that can be used to tell a cancerous group of cells apart from normal ones. These are:

  • Avoiding cell death (apoptosis)
  • Resistance to anti-growth signals
  • Signal to themselves to grow
  • Invade tissue and metastasise (spread to other parts of the body)
  • Can replicate infinitely
  • Form new blood vessels



Cancer in one part of the body can metastasise – spread to another part of the body. For example, if there is a tumour in a patient’s liver, it might spread to the lungs. There are a few ways that cancer can spread. Cancer cells can travel through the blood vessels to a different part of the body and settle there. They can do the same thing through the lymphatic system: this system filters body fluid back to your heart and contains many immune cells for fighting infection. Just like your circulatory system, this system also extends all over the body. Once a cancer has metastasised, it is often harder to treat, so it is important to catch cancer early. 

You cannot catch cancer like you can catch chickenpox. The cause originates inside your body. You might have heard that cancer is a genetic disease. Ultimately, cancer is always caused by mutations in the DNA of a cell. Mutations refer to changes in the DNA. This often means the DNA is damaged, which is the case in cancer, but mutations are sometimes ‘silent’ meaning the change to the DNA has no effect. Mutations can be inherited, caused by environmental factors or can happen randomly. 

There are environmental factors called carcinogens that can cause the DNA in cells to become damaged over time. Some examples are smoking, x-rays, UV radiation from the sun and some chemicals in our environment. Usually our cells can repair damaged DNA, and if it is too badly damaged it dies. Even if some cells with damaged DNA do not manage to do either of these 2 things, the immune system usually recognises the abnormal cells and destroys them.

Genes are made up of DNA and faulty genes can be inherited from your parents. Genes code for certain characteristics and when mutated, they can cause things to go wrong. What exactly goes wrong or does not work properly depends on the usual function of the gene. There are 4 key groups of genes that can lead to cancer when damaged.

Oncogenes instruct cells to divide. This is normally important for growth and repair. However when an oncogene is damaged, it is constantly telling the cell to divide, causing a cancer. Tumour suppressor genes stop cells from dividing if the cell has damaged DNA. When tumour suppressor genes are damaged, the cell does not respond to instructions to stop dividing, so a cancer forms.

DNA repair genes usually repair any damaged DNA in cells. When these are damaged, the cell is less able to repair its DNA so mistakes in the DNA can build up over time. The last group of genes are self-destruct genes which tell the cell to die if it is too old or too damaged. When something goes wrong in a cell, it is usually instructed to self-destruct to avoid a cancer forming. However, when these genes are not working properly, damaged cells can survive and cause cancer.

You cannot directly catch cancer from someone else. However there are some pathogens – microbes that cause disease such as viruses and bacteria –  that you can catch that increase a person’s chance of causing certain cancers by damaging the DNA in the cells. Catching any one of these pathogens does not guarantee you will develop cancer, it just increases the chance that you will develop particular types. There are currently 11 known pathogens that promote cancer development. For some of these pathogens we have vaccines, for example the HPV virus that can cause many cancers and nearly all of cervical cancers. All year 8 students in the UK are now offered the HPV vaccine. 

How is cancer treated?

1 in 2 people in the UK will get cancer in their lifetime. Thanks to research, many types of cancer can now be cured, and ongoing research will improve treatments further in the future. How cancer is treated very much depends on the type of cancer and there are lots of different treatment options available. Some of the most common treatments are surgery – to remove the cancerous tumour, chemotherapy – an anti-cancer drug treatment, and radiotherapy – using radiation to damage the DNA in cancer cells so badly that the cells die. To find out more about cancer and how it is treated, check out Cancer Research UK.