AQA A Level Biology

Revision Notes

8.2.10 Two Types of Tumours

The Characteristics of Benign & Malignant Tumours

  • Tumours are groups of abnormal cells that form lumps or growths
  • They can start in any of the cells in our bodies
  • Tumours have different characteristics depending on whether they are cancerous (malignant) or non-cancerous (benign)
  • All tumours may cause harm to the body by:
    • Damaging the organ in which the tumour is located
    • Causing blockages or obstructions
    • Damaging other organs by exerting pressure

Malignant tumours

  • Malignant tumours are cancerous
  • Malignant tumours cause cancer by growing rapidly, then invading and destroying surrounding tissues
  • Cells within malignant tumours secret chemicals that cause the formation of blood vessels to supply the tumour with nutrients, growth factors and oxygen
  • Cells can break off these tumours and spread to other parts of the body through the bloodstream or lymphatic system, this is called metastasis
  • Metastasis causes the spread of tumours to other places in the body, affecting multiple organs
  • When removed through surgery, malignant tumours can still grow back
  • The formation of malignant tumours can be initiated by carcinogens such as:
    • UV or X-ray exposure
    • Tobacco from cigarettes
    • Asbestos
    • Processed meat

Benign tumours

  • Benign tumours are not cancerous
  • These tumours grow slowly 
  • Benign tumours do not invade other tissues and do not metastasise, unlike malignant tumours
  • These tumours can cause damage such as blockages or by exerting pressure on the organ it is growing in or those surrounding it
  • When removed, benign tumours do not usually grow back
  • The formation of benign tumours can be initiated by:
    • Inflammation or infection
    • Injury
    • Diet
    • Genetics
    • Toxins and radiation
  • Examples of benign tumours are:
    • Polyps found in the nose, colon and ovaries
    • Non-cancerous brain tumours
    • Warts, caused by a viral infection

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