What is cancer?

Expert reviewer, Mr Robin Crawford, Consultant Gynaecological Oncologist
Next review due December 2020

Cancer is the name given to a group of over 200 related diseases. If you have cancer, some of your cells begin to grow in an uncontrolled way and may spread into other tissues. Cancer can start almost anywhere in your body.

Half of us will get cancer at some point in our lives – most likely in old age. Although it’s usually a serious condition, many people are cured and more than half will live for over ten years. Research is going on all the time to help doctors improve how they diagnose and treat cancer.

If you or someone you care for has cancer, you may find it helps to learn more about the condition. Here we give you some very general information about cancer, and some links to our other cancer information. We also give details of organisations which offer more information, advice and support for those with cancer and their carers.

A doctor showing a senior patient a leaflet in his office

About cancer

Your body is made up of many different types of cells that form your tissues and organs. These cells normally grow and divide in a controlled way. This is how your body grows and repairs itself. However, cancer cells don’t stop dividing – they carry on growing. Often they form lumps, and these are called tumours. Not all cancer cells form solid tumours. An example is leukaemia – cancer of the blood-forming cells in bone marrow.

Cancer cells can invade surrounding tissues. They can also spread to form secondary tumours in other parts of your body. This spreading process is called metastasising, and you may hear secondary tumours being referred to as metastatic cancer.

Symptoms of cancer

The symptoms of cancer can vary widely depending on the specific type you have, but there are certain symptoms to look out for. These include the following.

  • A new lump in any area of your body – for example in women, a lump in your breast, or in men, in your testicle.
  • Any unusual bleeding – for example blood in your urine, vomit or faeces (stool).
  • Coughing up blood, or a cough that just won’t go away.
  • A sore that won’t heal. This can be anywhere on your body including your mouth and genitals.
  • Unexplained weight loss.
  • Changes to a mole, such as bleeding, itching or a change in size or colour.
  • A change in your usual bowel habits – for example constipation or diarrhoea which goes on for more than three weeks.

Remember – these are often caused by other medical conditions which aren’t cancer. But if you have any of these symptoms, or notice other unusual changes in your body which don’t go away, contact your GP.

You may like to read our health blogs, Mole checks: spotting the signs of skin cancer early and ‘Symptoms of bowel cancer and reducing your risk’. See also our factsheet on breast cancer symptoms.

Cancer screening

You can have early cancer without any symptoms. That’s why it’s important to consider having screening tests if your GP recommends them. Depending on your age and gender these might include tests for cancer of the cervix, breast and bowel. Screening for cancer aims to find it at an early stage when treatment is more likely to be successful.

You may like to read our information on breast screening and cervical screening.

Diagnosis of cancer

If you have symptoms, your GP will ask about these and may examine you. They may also ask about your medical history and about cancer in other members of your family. Your GP may offer you tests to find out whether your symptoms may be due to cancer or are caused by another condition. These tests may include:

If your GP thinks you may have cancer, they’ll refer you to a specialist. You’ll usually be seen within two weeks.

You may need other tests depending on your symptoms and the area of your body that’s affected. For example, your GP or specialist doctor may arrange for you to have an examination using an endoscope to look into your stomach or bowel.

You may also need to have a biopsy taken. A biopsy is a small sample of your tissue which is sent to a laboratory to look for cancer cells.

If you’re found to have cancer, you may need to have other tests to see how big the cancer is and whether it has spread. This is called staging. Staging is important because it helps your doctor work out what the best course of treatment will be for you.

If your doctor recommends any tests, they’ll explain why the test is important and what it involves. It’s OK to ask questions and it’s important to raise any concerns you have.

Treatment of cancer

Your treatment will depend on the specific type of cancer you have and if it has spread. You may have treatment to:

  • cure the cancer
  • shrink or slow down the cancer growth to prolong your life
  • reduce the symptoms caused by the cancer – this is called palliative therapy

Surgery to remove the tumour is a common treatment for cancer but your doctor may also offer you chemotherapy and radiotherapy. Other treatments include immunotherapy (using your immune system to fight cancer), hormone therapy (helps stop the tumour growing) and targeted therapies (to target cancer cells). Targeted therapies may be based on your genetic makeup, as we know some cancers are linked to your genes. Your doctor may, in some circumstances, recommend a bone marrow (stem cell) transplant. You may need to have more than one type of treatment.

Your doctor will discuss these treatments with you and go through your possible choices. They may also ask whether you’d like to take part in a clinical trial to help find out if a new treatment works.

You may like to read our factsheet, Adjusting after cancer treatment.

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Who’s who in cancer

If you have cancer, you’re likely to meet many different doctors and health professionals during your care. They’ll each have a different expertise in cancer and together can provide the best treatment for you.

  • Cancer nurse specialist – your main point of contact during and after your cancer treatment. They are nurses with in-depth knowledge in the specific area of cancer care.
  • Oncologist – a doctor who specialises in cancer care and has advanced knowledge and understanding of cancer treatments. Oncologists treat cancer using methods other than surgery, including chemotherapy and radiotherapy.
  • Surgeon – a doctor who specialises in carrying out operations to treat an injury or condition. When treating cancer, different surgeons will specialise in operating on specific parts of the body.
  • Radiographer. A diagnostic radiographer uses techniques such as X-ray, MRI and CT scans, to take images. A therapeutic radiographer operates the machine that delivers your radiotherapy treatment.
  • Radiologist – a doctor who specialises in using imaging methods to diagnose medical conditions, including cancer.
  • Dietitian – can give you advice on healthy eating especially if you’re having trouble eating and drinking because of your cancer treatment.
  • Physiotherapist – a health professional who specialises in maintaining and improving movement and mobility.
  • Psychologist or counsellor. A psychologist is a health professional who specialises in emotional and behavioural problems; a counsellor is a health professional who also provides emotional support.
  • Pharmacist – prepares and checks the type and dose of medicine that your doctor prescribes. They can also advise you on how to take your medicine and the possible side-effects you may have.
  • Occupational therapist – a health professional who can give practical assistance to help you manage everyday activities and increase your independence.
  • Histopathologist – a doctor who examines samples of tissue under a microscope to help diagnose a disease such as cancer.
  • Physicist – an expert in radiation who will help to plan your radiotherapy treatment.

And of course, you’ll be supported throughout by your GP. They may arrange your first tests, refer you to a specialist and be involved in looking after any general problems you have during your treatment. Your GP may also need to liaise with different members of your medical team during your treatment.

Types of cancer

Cancers are named after the types of cells they develop from. We describe the three main groups here, but there are many other types.


Carcinomas are by far the most common types of cancer. This type of cancer starts off in epithelial cells. These are cells that cover surfaces and line your organs and tissues. Common carcinomas include cancers of the breast, lung, prostate and bowel. Together these four cancers alone make up over half of all new cancers each year, and overall, 85 out of 100 cancers are carcinomas.


This type of cancer develops from the cells of your connective tissues which support your organs. These include bone, muscle, blood vessels and fat. The two main types are bone sarcomas and soft tissue sarcomas. Sarcomas are rare; fewer than one in 100 diagnosed cancers are sarcomas.

Leukaemias and lymphomas

These are cancers of your blood and lymphatic system. In leukaemia your bone marrow makes too many white blood cells, which are abnormal and don’t work properly. Lymphomas are cancers starting in your lymphatic system, which includes your lymph nodes and lymph vessels. These tissues help you fight infections. Only about eight in 100 people diagnosed with cancer have leukaemia or lymphoma. But although they’re quite rare, leukaemias are the most common type of cancers in children.

Information about specific cancers

We have a range of factsheets covering the most common forms of cancer. See the links below or find them in our A–Z of topics.

Causes of cancer

Most cancers are thought to be caused by a combination of factors, including the following.

  • Age. Your risk of cancer increases with age. Half of newly diagnosed cancers happen in people aged 70 or over.
  • Smoking. This is the main cause of lung cancer and increases your risk of getting many other cancers.
  • Family history. You may be more likely to get some types of cancer if your family members have had them. This is because you can inherit genes that make cancer more likely to develop. Speak to your GP about whether you should have any additional screening tests.
  • Food and drink. A diet high in animal fats and red/processed meat but low in fruit and vegetables increases your risk of getting certain types of cancer. If you drink excessive amounts of alcohol or are overweight, it can also increase your risk.
  • Being inactive. If you aren’t physically active you have a higher risk of some types of cancer including breast and bowel cancer.
  • Sun exposure. Ultraviolet (UV) rays can increase your risk of getting certain cancers. Prolonged exposure to the sun, or using a sun bed often, is known to cause skin cancer, including melanoma.
  • Infections. Certain infections can increase your risk. For example, a virus called human papilloma virus (HPV) can increase your risk of getting cervical cancer.
  • Cancer-causing substances. Exposure to certain substances that are known to cause cancer (carcinogens), such as asbestos and radioactive materials, can increase your risk.

It’s thought that about half of all cancers are preventable. You can reduce your risk of getting cancer by making healthy lifestyle changes.

Cancer isn’t infectious and you can’t catch it from other people.

You may like to read our health blogs:

Help and support

Being diagnosed with cancer can be distressing for you and your family. An important part of cancer treatment is support to deal with the emotional aspects as well as the physical symptoms. Specialist cancer doctors and nurses are experts in providing the support you need. Talk to your doctor or nurse if you’re finding your feelings hard to cope with.

Everyone has their own way of coping. But for further support and advice you may find it helpful to contact one of the well known cancer organisations or visit their websites. They have information about most types of cancer – often in more detail than we can go into here. Some have a telephone helpline you can ring, or an online forum you can join for a chat with others in your position. There may also be local groups where you can meet other people with similar medical issues, or other carers. Your cancer team may know of some.

See our section ‘other helpful websites’ below for contact details of relevant organisations. You may also find our general cancer articles helpful. These include the following.


Frequently asked questions

  • The most common cancer in the UK is breast cancer, followed by lung, prostate and bowel cancer. Over half of all people who are newly diagnosed with cancer have one of these types.

    For every 100 women who have cancer:

    For every 100 men who have cancer:

    • 26 have prostate cancer
    • 14 have lung cancer
    • 13 have bowel cancer
    • 48 have other cancers (including cancer of the head and neck, cancer of the kidney and melanoma)

  • It can be very upsetting if someone you know has been diagnosed with cancer, but there are lots of things you can do to help.

    If a friend has cancer, it can be a very difficult time for both of you. Talking to your friend will help you to understand better how they’re feeling and coping with the illness. Be realistic about how much time you can spend with your friend. Try to be reliable, too, so they know how much they can depend on you.

    You may find it hard to talk to your friend at first, as they may act as if everything is normal. If your friend doesn’t feel ready to talk, carry on with life as normal but offer your support. Look for information about the type of cancer your friend has to help you understand what they’re going through. But remember it can be different for different people.

    Respect your friend’s privacy if they don’t want to talk about their cancer to you or to other people. Just being there and continuing to stay in touch and talking about normal things can be a support. Many people like to try and keep their lives as normal as possible when they’re having treatment for cancer.

    It’s important to check that your friend actually wants your help. Try to think about specific practical ways you can help rather than just asking if there’s anything you can do. Perhaps offer to cook a meal, pick up the children from school or do some shopping. You could also offer to accompany your friend to medical appointments or treatment sessions. Be sensitive if your friend doesn’t want support – let them know the offer is still available if things change later.

    Remember to take time out for yourself, as supporting somebody with cancer can be stressful and upsetting. Talk to other people about how you’re feeling and make sure others are involved with caring too. There are many support groups that offer help and advice for friends and family of people with cancer. See our section ‘other helpful websites’ below for useful contact details.

  • Cancer can be cured in many cases, but not always. Whether you can be cured depends on a number of things. These include the type of cancer you have, how early it’s diagnosed and your age and general health. Everyone is different. Your doctor will be able to talk to you about the chances of a cure in your particular circumstances.

    Different cancers respond to different treatments so there isn’t going to be one treatment that will be ‘a cure for cancer’. There are over 200 different types of cancer and some are easier to cure than others.

    For most cancers, if you’re diagnosed at an early stage there’s a better chance of you being cured. That’s why you should contact your GP as soon as possible if you have a symptom you’re worried about.

    If your cancer can’t be cured, there are usually treatments which will give you many extra months or years of good quality life. And treatment can relieve the symptoms of cancer.

    You may find that your doctor prefers to say your cancer is ‘in remission’ rather than being cured. Remission means that there are no signs of cancer in your body, but your doctor can’t say for sure that it will never come back. This is because some cancers can come back many years after they seem to have gone.

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Related information

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  • Reviewed by Dr Kristina Routh, Freelance Health Editor, Bupa Health Content Team, December 2017
    Expert reviewer, Mr Robin Crawford, Consultant Gynaecological Oncologist
    Next review due December 2020