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Cancer - an overview

Published by Bupa's health information team, July 2009.

This factsheet is for people who have cancer, or would like information about it.

Cancer is caused by cells in the body changing so that they grow in an uncontrolled way. It's estimated that one in three people will get cancer at some point in their lives.

How cancer develops

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About cancer

Your body is made up of different types of cells that form your organs such as your heart and liver, and tissues like your muscles.

Cells reproduce by dividing in a controlled way and this is how your body grows and repairs itself. Cancer cells don't stop dividing but instead carry on to form a tumour. Scientists believe this happens when something goes wrong with the mechanism inside the cells that usually tells them to stop reproducing.

Tumours can become detached and spread to other areas of the body. There are two main types of tumour: benign and malignant. Malignant tumour is another term for cancer.

Benign tumours

Tumours that don't invade other tissues or spread to other parts of the body are known as benign. Benign tumours aren't cancerous. They usually grow slowly and are made up of cells that are very similar to normal cells. As a benign tumour gets bigger, it takes up more space, pressing on the organs and tissues next to it.

Malignant tumours

Tumours that invade surrounding tissue and spread to other parts of the body are known as malignant. Malignant tumours are cancerous. They are usually more aggressive and grow faster than benign tumours. They can spread through the bloodstream and lymphatic system to other parts of the body to form secondary tumours. This is called metastasis.

Types of cancer

There are about 200 different types of cancer affecting all the different body tissues. They are named by the types of cells that they develop from.

Carcinoma

This type of cancer starts off in the epithelial cells that line the organs and tissues. Lung cancer, prostate cancer, breast cancer and stomach cancer are all carcinomas. Up to 85 in 100 diagnosed cancers are carcinomas. The different types of carcinoma depend on the type of epithelial cell they come from.

There are four main types of epithelial cells:

  • squamous cells - flat cells lining the skin, mouth, oesophagus (food pipe) and the airways
  • adenomatous cells - glandular cells lining organs that contain glands, including the stomach, bowel, pancreas, kidneys, prostate gland, ovaries and breasts
  • transitional cells - found in the bladder and urinary tract
  • basal cells - found in one of the layers of the skin

So, for example, a cancer that starts in squamous epithelial cells is called a squamous cell carcinoma.

Sarcoma

This type of cancer begins in the cells of supportive tissues. Sarcomas make up less than one in 100 of diagnosed cancers.

The two main types are:

  • bone sarcomas
  • soft tissue sarcomas

Leukaemia and lymphoma

These cancers begin in white blood cells (part of the body's defence system) in the bone marrow and lymphatic system. Some types of blood cancer are more common in children than adults.

Others

Other, rarer forms of cancer include brain and spinal tumours.

Cancers that develop from different cell types behave differently - for example, certain cell types are more likely to grow quickly and spread than others.

Causes of cancer

Most cancers are thought to be caused by a combination of risk factors. One of the biggest is increasing age - about two-thirds of all newly diagnosed cancers occur in people aged 65 or over.

Others include:

  • smoking - a major cause of lung cancer, and a factor in bladder cancer and head and neck cancers among others
  • your genes - you may be more likely to get some types of cancer if family members have had them
  • diet - eating a diet high in animal fats, red and processed meat and low in fruit and vegetables, being overweight and drinking excessive amounts of alcohol
  • ultraviolet (UV) rays - prolonged exposure to the sun is known to cause skin cancer
  • infection - for example, a virus called human papilloma virus (HPV) is thought to increase the risk of cervical cancer
  • exposure to cancer-causing substances (carcinogens) - these include asbestos, benzene and radioactive materials
  • a weak immune system - because of medicines that suppress your immune system (for example, those taken for organ transplants), high doses of radiation (radiotherapy), or diseases that weaken your immune system, including the human immunodeficiency virus (HIV)/AIDS

Cancer isn't infectious and can't be caught from other people.

Diagnosis of cancer

Tests include blood tests, X-rays, MRI, CT and ultrasound scans, cystoscopy and endoscopy, depending on your symptoms and the area affected.

You will probably need to have a biopsy. This is a small sample of tissue which will be sent to a laboratory for testing to determine the type of cells and if these are benign or cancerous.

Primary and secondary cancer

The place where the cancer starts is called the primary cancer. Cancer cells can move through your blood vessels and lymphatic system and spread (metastasise) to other parts of your body to form more tumours. These are called secondary tumours.

Grading and staging

Grading and staging systems are used to classify cancers to work out how your cancer is likely to behave, and what the best treatment options will be. Scans such as a CT or MRI and biopsy are used to determine the grade and stage of your cancer.

Grades of cancer

The grade of cancer means the way the cells look under a microscope. The lower the grade, the more like a normal cell the cancer cell looks.

Healthy cells are specialised for the different jobs they do in your body. This is called differentiation. Cancer cells tend to be unspecialised or poorly differentiated.

Cancer can be divided into the following grades.

  • Grade 1 - low grade, or well differentiated, where cells look similar to healthy ones. It grows more slowly and is less likely to spread to other parts of the body.
  • Grade 2 - medium grade, or moderately differentiated, where cells look moderately different from healthy ones.
  • Grade 3 - high grade, or poorly differentiated, where cells look very different from healthy ones. It grows more quickly and is more likely to spread to other parts of your body.

Staging

Staging describes how advanced the cancer is, how large the primary tumour is, and whether it has invaded nearby tissues and spread to other parts of the body. There are several different staging systems depending on the type of cancer. Doctors sometimes use the term 'early stage' to describe a cancer that hasn't spread yet, and 'late' or 'advanced stage' for cancer that has spread to other organs. Examples of staging systems include:

  • TNM (tumour, node, metastasis) staging system
  • Dukes staging (A, B, C, or D) - commonly used to describe how advanced bowel cancer is

Treatment of cancer

Your treatment will depend on the specific type of cancer, the grade and stage. The most common treatments are surgery to remove the cancer, or other treatments such as chemotherapy and radiotherapy. Other, newer or experimental treatments include hormone therapy, gene therapy, biological therapy including immunotherapy, and bone marrow and stem cell transplants. Treatment may be given to:

  • cure the cancer
  • increase the chance of cure following surgery (adjuvant treatment)
  • shrink or slow down the cancer to prolong life
  • reduce symptoms caused by the cancer

There is a lot of uncertainty with cancer treatments, so doctors won't always be able to tell you exactly what will happen to you.

If you have been diagnosed with cancer, don't worry about asking your doctor or nurse to explain things to you several times using language that you understand rather than medical terms.

Write down questions or concerns you have before appointments and make notes of important points. You can also take someone along for support. After your appointment, your doctor will send a letter to your GP and you will often be able to have a copy of this if you would like one.

For more information on treatments for specific cancers, please see the separate Bupa health factsheet on the type of cancer you would like to find out about.

Help and support

Being diagnosed with cancer can be distressing for you and your family. Dealing with the emotional aspects, as well as the physical symptoms, is an important part of treatment. Specialist cancer doctors and nurses are experts in providing the support you need, and may visit you at home. If you have more advanced cancer, further support is available to you in hospices or at home - this is called palliative care.

Related topics

Further information

Sources

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: July 2009

 

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