Two Types of Tumours (AQA A Level Biology): Revision Note

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, which 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 in which it is growing 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