Authored by Dr Gurvinder Rull, 14 Nov 2017

Patient is a certified member of
The Information Standard

Reviewed by:
Dr Hannah Gronow, 14 Nov 2017

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.

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. However, there are often great differences between different types of cancer. For example:

  • Some grow and spread more quickly than others.
  • Some are easier to treat than others, particularly if diagnosed at an early stage.
  • Some respond much better than others to chemotherapy, radiotherapy, or other treatments.
  • Some have a better outlook (prognosis) than others. For some types of cancer there is a very good chance of being cured. For some types of cancer, the outlook is poor.

So, cancer is not just one condition. In each case it is important to know exactly what type of cancer has developed, how large it has become, whether it has spread and how well the particular type of cancer responds to various treatments. This will enable you to get reliable information on treatment options and outlook. Read more about cancer symptoms.

A tumour is a lump or growth of tissue made up from abnormal cells. Tumours are divided into two types: benign and malignant.

Non-cancerous (benign) tumours

These may form in various parts of the body. Benign tumours 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 tumours can cause problems. For example, some grow quite large and may cause local pressure symptoms, or look unsightly. Also, some benign tumours that arise from cells in hormone glands can make too much hormone, which can cause unwanted effects.

Cancerous (malignant) tumours

Malignant tumours tend to grow quite quickly, and invade into nearby tissues and organs, which can cause damage. Tumours 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). This happens if some cells break off from the primary tumour and are carried in the bloodstream or lymph channels to other parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.

Note: not all cancers form solid tumours. For example, in cancer of the blood cells (leukaemia) many abnormal blood cells are made in the bone marrow and circulate in the bloodstream.

Read more about types of 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 cancerous (malignant) tumour.

We all have a risk of developing cancer. Many cancers seem to develop for no apparent reason. However, certain risk factors are known to increase the chance that one or more of your cells will become abnormal and lead to cancer. Read more about cancer causes.

You may develop symptoms such as a lump, weight loss or loss of appetite. The symptoms for each type of cancer vary according to the type of cancer. For example, lung cancer may present with a cough and bowel cancer may present with blood in the stool.

Due to the significant poor outcomes from some cancers there are also cancers which will be picked up on routine testing called 'screening'. Examples of this include mammograms looking for breast cancer and home stool screening for bowel cancer.

Based on how you present, further tests will usually be necessary. This may include scans and taking a sample of the cancer and analysing it in the laboratory (biopsy). Read more about diagnosing 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. Cancer is classified depending on its type (grading) and how far it has spread in the body (staging). This will affect treatment options.

The three most common treatments are:

  • Surgery - operative removal of the cancer.
  • Chemotherapy. Use of anti-cancer medicines to kill cancer cells, or to stop them from dividing. Medicines can be used alone or in various combinations. Read more about chemotherapy.
  • Radiotherapy. Use of radiation beams directed at cancerous tissue. Radiotherapy can kill cancer cells, or stops them multiplying. Read more about radiotherapy.

There are also more specialised treatments. Read more about cancer treatment.

  • Some cancers are more aggressive and grow more quickly than others.
  • Some cancers are more likely to spread to other parts of the body.
  • Some cancers respond to treatment better than others.

Therefore, it is not possible to give an overall outlook (prognosis). See the information about the individual types of cancer for further details. As a general rule, the outlook is usually better the earlier a cancer is detected and treated. Read more about cancer prognosis.

Further reading and references

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