Cancer - A General Overview


Cancer is a disease of the cells in the body. There are many different types of cell in the body, and many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply out of control.

Normal body cells

The body is made up from millions of tiny cells. Different parts of the body such as organs, bones, muscles, skin, and blood are made up from different specialised cells. All cells have a centre called a nucleus. The nucleus in each cell contains thousands of genes which are made up from a chemical called DNA. The genes are like codes which control the functions of the cell.
Most types of cell in the body divide and multiply from time to time. As old cells wear out or become damaged, new cells are formed to replace them.
Abnormal cells
Sometimes a cell becomes abnormal. This occurs because one (or more) gene in the cell becomes damaged or altered. Lots of abnormal cells may then develop from the original abnormal cell. These cells do not know when to stop multiplying.
Benign tumours
These may form in various parts of the body. Benign tumors grow slowly, and do not spread or invade other tissues. They are not cancerous and are not usually life-threatening. They often do no harm if they are left alone. However, some benign tumors can cause problems. For example, some grow quite large and may cause local pressure symptoms, or look unsightly.
Malignant tumors
Malignant tumors tend to grow quite quickly, and invade into nearby tissues and organs, which can cause damage. Tumors normally develop in one original site - the primary tumour. Malignant tumours may also spread to other parts of the body to form secondary tumours (metastases).
What causes cancer?
Each cancer is thought to first start from one abnormal cell. What seems to happen is that certain vital genes which control how cells divide and multiply are damaged or altered. This makes the cell abnormal. If the abnormal cell survives it may multiply out of control into a malignant tumour.

Risk factors include the following:

Chemical carcinogens
A carcinogen is something (chemical, radiation, etc) that can damage a cell and make it more likely to turn into a cancerous cell.
Tobacco smoke.
Workplace chemicals such as asbestos, benzene, formaldehyde, etc.
Diet and other lifestyle factors:

  • If you eat a lot of fruit and vegetables you have a reduced risk of developing certain cancers.
  • Eating too much fatty food possibly increases the risk of developing certain cancers.
  • The risk of developing certain cancers is increased by: obesity, lack of regular exercise (physical activity), and drinking a lot of alcohol.


  • Some viruses are linked to certain cancers. For example, people with persistent infection with the hepatitis B virus or the hepatitis C virus have an increased risk of developing cancer of the liver. Another example is the link between the human papillomavirus (HPV) and cervical cancer.

Immune system
People with a poor immune system have an increased risk of developing certain cancers. For example, people with AIDS, or people on immunosuppressive therapy.
How is cancer diagnosed?
If a cancer is suspected from your symptoms. Your doctor will examine you to look for abnormalities such as a lump under the skin, or an enlarged liver. You may be referred for tests such as X-rays, scans, blood tests, endoscopy, bronchoscopy, etc, depending on where the suspected cancer is situated. These tests can often find the site of a suspected cancer. However, a biopsy is often needed to be certain that the abnormality is a cancer and not something else (such as a benign tumour).

What are the treatment options for cancer?
Treatment options vary, depending on the type of cancer and how far it has grown and spread. See the separate leaflets on the specific cancers for more details.

  • Surgery.
  • Chemotherapy. This is a treatment that uses anticancer drugs to kill cancer cells, or to stop them from multiplying.
  • Radiotherapy. This is a treatment that uses high-energy beams of radiation which are focused on cancerous tissue.

More recently, other treatments have been introduced which include:

  • Bone marrow transplant. High-dose chemotherapy may damage bone marrow cells and lead to blood problems. However, if you receive healthy bone marrow after the chemotherapy then this helps to overcome this problem.
  • Hormone therapy. This is where drugs are used to block the effects of hormones. This treatment may be used for cancers that are hormone-sensitive such as some cancers of the breast, prostate and uterus.
  • Immunotherapy. Some treatments can boost the immune system to help to fight cancer.
  • Gene therapy. This is a new area of possible treatments. Research is underway to find ways of blocking, repairing or replacing abnormal genes in cancer cells.
  • Special techniques. These can sometimes be used to cut off the blood supply to tumours. The tumour then dies.

What are the aims of treatment?
The aims of treatment can vary, depending on the cancer type, size, spread, etc. For example:
Treatment aims to cure the cancer in many cases. With modern drugs and therapies, many cancers can be cured, particularly if they are treated in the early stages of the disease. Doctors tend to use the word remission rather than the word cured. Remission means there is no evidence of cancer following treatment. If you are in remission, you may be cured. However, in some cases a cancer returns months or years later.
Treatment may aim to control the cancer. If a cure is not realistic, with treatment it is often possible to limit the growth or spread of the cancer so that it progresses less rapidly. This may keep you free of symptoms for some time.
Treatment may aim to ease symptoms in some cases. Even if a cure is not possible, a course of radiotherapy, an operation, or other techniques may be used to reduce the size of a cancer,which may ease symptoms such as pain.

What is the outlook for people with cancer?
Some cancers are more aggressive and grow more quickly than others. Some cancers are more likely to spread to other parts of the body.
Therefore, it is not possible give an overall outlook (prognosis).
Questions you may want to ask your doctor

  • What type of cancer have I got?
  • How large is it and has it spread to other parts of my body?
  • What are the treatment options for this type of cancer?
  • What are the risks and possible side-effects of the treatment options?
  • How successful is the treatment for my type and stage of cancer? Is the aim of treatment to cure or to control the cancer?

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