Cancer is not one disease but many. It begins when cells in the body start to grow and divide in ways they shouldn’t — and understanding that basic idea makes everything else easier to follow.
Cancer is a group of diseases in which some of the body’s cells grow uncontrollably and can spread into surrounding tissue or to other parts of the body. Normally, cells grow, divide and die in an orderly way. In cancer, that orderly process breaks down: abnormal cells survive when they should die, and keep multiplying.
These changes usually build up gradually, often through damage to the instructions inside a cell. Many things can contribute. Some are within our influence — such as tobacco, alcohol or sun exposure — and some are not, such as age or inherited risk. This is why prevention matters, but also why cancer is never simply someone’s “fault”.
A tumour is simply a lump or growth of tissue. A benign tumour is not cancer and usually stays where it is. A malignant tumour is cancer and can spread. You’ll find clear definitions of these and more in our glossary.
• What type of cancer is this, exactly?
• What does the stage or grade mean?
• What are my options, and what do they involve?
• Where can I find reliable information about it?
• What is cancer, really?
• How does it start and spread?
• What do the common words mean?
What is cancer?
How it develops
Words you’ll hear
Questions to ask
This guide is based on public guidance from European cancer institutes and public health authorities, written in plain language.
