Cancer: tumours, risk factors and data

How a tumour forms

Cancer is the result of changes in cells that lead to uncontrolled growth and division.

The cells divide by mitosis again and again, without the normal checks, and form a lump called a tumour.

• Benign tumour: growths of abnormal cells contained in one area, usually within a membrane. They do not invade other parts of the body. They can still be harmful, for example by pressing on the brain.
• Malignant tumour: a cancer. Its cells invade neighbouring tissues and can spread to different parts of the body in the blood, where they form secondary tumours.

1. Tumour cells divide once every 24 hours, starting from 5 cells
2. In 10 days: 10 × 24 = 240 hours; 240 ÷ 24 = 10 divisions
3. Cells = 5 × 2¹⁰ = 5 × 1024 = 5120
4. = 5.12 × 10³ cells

Each division doubles the number: multiply by 2 once for every division (2¹⁰), not by 2 × 10.