Cancer: Students should be able to describe cancer as the result of changes in cells that lead to uncontrolled growth and division.

The idea

Cancer begins when changes in a cell's genetic material alter the control of the cell cycle. Normally, cell division is regulated so that new cells are produced only when needed for growth or repair. After these changes, the cell divides repeatedly without responding to the usual controls, producing an uncontrolled growth and division that forms a mass of abnormal cells called a tumour. Tumours that invade neighbouring tissues and spread to other parts of the body through the blood or lymph are malignant and are described as cancer. Benign tumours grow in one place and do not invade or spread. Risk factors such as smoking, obesity, ultraviolet radiation and some viruses increase the chance of the cell changes occurring, but they do not guarantee that cancer will develop.

What earns the marks

• State that cancer results from changes in cells, often described as mutations in the genetic material.
• Explain that these changes affect the control of cell growth and division, so the cell cycle is no longer regulated normally.
• Describe the outcome as uncontrolled growth and division, producing a mass of abnormal cells called a tumour.
• Distinguish malignant tumours, which invade neighbouring tissues and spread to other parts of the body, from benign tumours, which do not.
• Link named risk factors, such as smoking, obesity, ultraviolet radiation or viral infection, to an increased chance of the cell changes occurring.
• Explain that a tumour forms when abnormal cells continue to divide rather than being removed or controlled by the body.
• Use the terms cell division, uncontrolled growth, tumour and malignant accurately when describing cancer.

Common mistakes and how to put them right

• Writing that cancer is a single disease caused by one mutation.

  Put it right by saying cancers result from changes in cells, and several changes are usually needed.

• Saying that all tumours are cancerous.

  Put it right by distinguishing benign tumours, which stay in one place, from malignant tumours, which invade and spread.

• Claiming that a risk factor such as smoking always causes cancer.

  Put it right by saying it increases the risk or chance of the cell changes occurring.

• Describing cancer as uncontrolled cell growth without mentioning division.

  Put it right by including both growth and division of cells.

Exam tips

• Use the phrase changes in cells that lead to uncontrolled growth and division, then add detail about tumours to secure the explanation.
• When a question names a risk factor, link it to an increased chance of cell changes rather than to a guaranteed outcome.
• If asked to compare tumour types, give one clear difference such as malignant tumours spread while benign tumours do not.
• Keep answers focused on cells and the cell cycle rather than on treatments, unless the question specifically asks about treatment.