Cells and organisation · GCSE Biology
Cancer and tumours
Explain cancer for GCSE Biology: uncontrolled mitosis, benign versus malignant tumours, secondary tumours (metastasis), and lifestyle and genetic risk factors in Combined and Triple language.
Cancer is the cell cycle without the brakes: mitosis too often. Benign tumours stay put. Malignant tumours invade and can spread in blood to form secondary tumours.
The important bits
What you need to know
- 1
A tumour is a mass of cells produced by uncontrolled cell division (mitosis that is no longer properly regulated).
- 2
Benign tumours grow in one place, are often contained in a membrane, grow slowly, and do not usually spread. They can still be harmful if they press on an organ (for example in the brain).
- 3
Malignant tumours are cancers. Cells can invade neighbouring tissues and break off, travel in the blood or lymph, and form secondary tumours (metastasis) elsewhere.
- 4
Causes linked to cancer include ionising radiation (UV, X-rays), chemical carcinogens (tar in tobacco smoke), some viruses, and inherited faulty alleles that affect cell-cycle control.
- 5
Lifestyle factors that change risk: smoking (lung), UV exposure (skin), alcohol, obesity, and some diets. Correlation in data does not always prove causation, but smoking and lung cancer is a causal link with strong evidence.
- 6
Treatment ideas at GCSE: surgery to remove a tumour, radiotherapy to kill dividing cells, chemotherapy to stop the cell cycle. Healthy dividing cells (hair, gut lining) are also affected, which explains side effects.
- 7
Not every mutation causes cancer. Several changes often have to accumulate in genes that control the cell cycle. Most mutations have no effect; a few increase division rate.
- 8
Stem-cell and meristem links: tissues that divide often (skin, gut, bone marrow) are more at risk of copy errors. Plant galls are uncontrolled plant division but are not usually taught as human cancer.
Quotations worth analysing
Short evidence. Real method.
“Cancer is caused by uncontrolled cell division.”
Name mitosis or the cell cycle. “Cells go wrong” is too vague. Uncontrolled mitosis is the mechanism.
“Malignant tumours can invade neighbouring tissues and spread to form secondary tumours.”
Spread via blood or lymph is the difference from benign. Use the word secondary if the paper does.
“Benign tumours stay in one place and do not spread.”
Still mention they can damage by pressure. Benign is not the same as harmless in every location.
Go deeper
How do I compare benign and malignant in four marks?
Benign: cells remain in one mass, often encapsulated, slower growth, no secondary tumours, may be easier to remove surgically. Malignant: cells invade, can enter blood or lymph, form secondary tumours in lungs, liver or bone, harder to treat because of spread, still the same underlying process of uncontrolled mitosis. Both can kill if they destroy an organ’s function. Do not write that benign tumours are “not dangerous” as a blanket rule. Do not write that malignant tumours are caused by bacteria. Viruses can contribute to some cancers (for example HPV and cervical cancer), which is why some vaccines reduce cancer risk — a neat link to the infection topic. Finish with “uncontrolled cell division” so the mitosis page and this page stay connected.
Go deeper
How should I treat a graph of smoking and lung-cancer deaths?
Describe: as cigarettes per day increase, death rate from lung cancer increases (positive correlation). Explain: tar contains carcinogens that cause mutations in genes controlling the cell cycle, so mitosis becomes uncontrolled in lung tissue. Evaluate: correlation plus a mechanism plus studies that control other variables support causation here; one graph alone is weaker if smokers also differ in other ways. A time lag of decades means today’s deaths reflect earlier smoking. Giving up reduces risk but not always to the never-smoked baseline, because some mutations have already occurred. In the exam, “smoking is bad” scores nothing. Name tar or carcinogen, mutation, uncontrolled mitosis, lung cells.
Go deeper
Why do chemotherapy and radiotherapy hit hair and gut as well as the tumour?
They target rapidly dividing cells. Tumour cells cycle often, so they take more damage, but hair follicles and intestinal lining also rely on frequent mitosis, so they are collateral. That is a cell-cycle side-effect, not a separate mystery. Surgery works best when the tumour is still local (often benign, or malignant caught early). Once secondary tumours exist, systemic treatment is needed. Higher-tier papers may mention that DNA damage checkpoints normally stop the cycle; cancer cells ignore those checkpoints. You do not need gene names at GCSE. You do need to say the control of mitosis has failed and that spread distinguishes malignant disease.
See the idea in action
A mole is removed and described as a benign tumour of skin cells. Uncontrolled mitosis produced a lump, but the cells had not invaded or entered the blood, so no secondary tumours were expected. A malignant melanoma, by contrast, can invade and spread, forming secondary tumours in other organs. UV radiation can mutate DNA in skin cells and raise the chance of that uncontrolled division. Treatment of a localised benign lump is often surgery; a spread malignant tumour may need radiotherapy or chemotherapy as well.
Exam technique
Turn knowledge into marks
Define cancer as uncontrolled mitosis. Contrast benign (stays put) with malignant (invades, secondary tumours). For risk-factor data, describe the pattern then name carcinogen → mutation → uncontrolled division.
Common mistakes
Do not give these marks away
- 01
Saying benign tumours cannot cause harm, or that all tumours are cancer.
- 02
Writing that cancer is caused by a lack of cells, or mixing it up with infection by bacteria as the usual cause.
- 03
Describing malignant spread without mentioning blood, lymph or secondary tumours.
What is the difference between a benign tumour and a malignant tumour?
ABenign tumours spread in the blood; malignant tumours never divide
BBenign tumours stay in one place; malignant tumours can invade tissues and form secondary tumours
CBenign tumours are caused by viruses; malignant tumours are caused by osmosis
DThere is no difference except the name
Show the answer
Benign tumours stay in one place; malignant tumours can invade tissues and form secondary tumours. Both involve uncontrolled mitosis. Malignant tumours are cancers that can spread. Benign masses remain localised, though they can still press on organs.
Quick questions
If this is the bit you searched
What causes cancer in GCSE Biology?
Uncontrolled cell division (mitosis). Mutations in genes that control the cell cycle can be triggered by radiation, chemicals such as tar, some viruses, or inherited alleles.
What is a malignant tumour?
A cancerous tumour whose cells invade nearby tissues and may spread in the blood or lymph to form secondary tumours.
What is a benign tumour?
A tumour that stays in one place and does not spread. It can still be dangerous if it presses on an organ.
How does smoking increase the risk of lung cancer?
Tar contains carcinogens that can mutate DNA in lung cells so the cell cycle is no longer controlled and mitosis produces a tumour.