6.25 - Cancer

Benign and malignant tumours

• Cancer is a disease that arises when changes in a cell lead to abnormal, uncontrolled growth and division.
• These abnormal cells divide far faster than the body needs, building up into a mass of cells called a tumour.
• There are two types of tumour, and they behave very differently.

Benign tumours

• A growth of abnormal cells that stays contained in one area, usually held within a membrane (it is encapsulated).
• It grows until there is no more room, but does not invade or spread to other parts of the body.
• Not normally dangerous, and is not cancer.

Malignant tumours

• A malignant tumour is cancer, and its cells are not held in one place (it is not encapsulated).
• The tumour grows into and invades neighbouring healthy tissues.
• Cells can break off and be carried around the body in the bloodstream.
• Wherever these cells settle, they invade the tissue and grow into new tumours, called secondary tumours.
• Because malignant tumours spread and damage tissue throughout the body, they can be fatal.