Science
How does cancer work?
Cancer works as a disease where the body's own cells start dividing uncontrollably and refuse to die, forming tumors or spreading. Damage to the genes that normally control cell growth lets these rogue cells multiply and invade healthy tissue.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how cancer works.
Step by step
- 1Normally, cells grow, divide, and die in a controlled way.
- 2Gene damage can switch off those controls.
- 3Rogue cells then divide endlessly and ignore signals to die.
- 4They can form tumors and invade or spread ('metastasize').
- 5Causes include mutations from genetics, chemicals, radiation, and chance.
Frequently asked questions
- What causes cancer?
- Damage to the genes that control cell growth — from inherited mutations, carcinogens, radiation, or random copying errors — lets cells divide uncontrollably.
- Why is cancer hard to treat?
- Cancer cells are the body's own, so treatments that kill them can harm healthy cells too, and tumors can evolve resistance.
- What does it mean when cancer spreads?
- Cells break away and travel to other parts of the body (metastasis), seeding new tumors that are harder to treat.

