Cancer is a disease caused by UNCONTROLLED CELL DIVISION.
Normally, cell division is carefully regulated by genes that control the cell cycle — telling cells when to divide and when to stop.
Cancer begins when MUTATIONS occur in these regulatory genes:
The 'stop dividing' signals are ignored.
Cells keep dividing repeatedly, producing more and more abnormal cells.
A mass of cells — called a TUMOUR — accumulates.
Cancers can develop in almost any tissue of the body. Common types include: breast cancer, lung cancer, bowel cancer, prostate cancer, skin cancer (melanoma).
Benign vs Malignant Tumours
Not all tumours are cancerous. There are two types:
BENIGN TUMOUR:
Grows slowly and stays in ONE PLACE.
Does not invade surrounding tissues.
Cells remain enclosed in a capsule.
Does not spread to other parts of the body.
Usually not life-threatening — can often be removed by surgery.
Can cause problems if it presses on a vital structure (e.g. a benign brain tumour pressing on important brain regions).
MALIGNANT TUMOUR (CANCER):
Grows quickly and INVADES surrounding tissues.
Cells break away from the original tumour.
Travel through the BLOOD or LYMPH system.
Settle in other organs and form NEW TUMOURS — this spread is called METASTASIS.
Much harder to treat once it has spread.
Malignant tumours are the dangerous, life-threatening form.
Risk Factors for Cancer
Several factors increase the risk of developing cancer:
LIFESTYLE RISK FACTORS:
Smoking — strongly linked to lung cancer, mouth cancer, throat cancer, bladder cancer. Carcinogens in tobacco smoke damage DNA in cells.
Alcohol — linked to liver cancer, mouth and throat cancer.
Obesity — associated with bowel cancer, breast cancer, uterine cancer.
Poor diet — low fibre linked to bowel cancer; processed meat linked to bowel cancer.
ENVIRONMENTAL RISK FACTORS:
UV radiation — sunlight and sunbeds cause skin cancer by damaging DNA in skin cells.
Ionising radiation — X-rays, gamma rays and nuclear radiation can damage DNA.
Asbestos — fibres lodge in lung tissue and damage cells → mesothelioma (lung cancer).
Certain chemicals — industrial carcinogens.
GENETIC RISK FACTORS:
Some people inherit mutations in tumour suppressor genes (e.g. BRCA1/2 gene mutations increase breast and ovarian cancer risk).
Having a family history of certain cancers increases personal risk.
VIRAL RISK FACTORS:
HPV (Human Papillomavirus) — causes most cases of cervical cancer.
Hepatitis B and C viruses — linked to liver cancer.
Treatment of Cancer
Cancer is treated using several approaches, often in combination:
SURGERY:
Physical removal of the tumour.
Effective for localised (non-metastatic) tumours.
Cannot remove cancer that has spread throughout the body.
RADIOTHERAPY:
High-energy radiation (gamma rays or X-rays) is directed at tumour cells.
Damages the DNA of cancer cells → they cannot divide → they die.
Side effects: damages healthy cells near the tumour, causing fatigue, nausea, hair loss in the treatment area.
CHEMOTHERAPY:
Drugs that target rapidly dividing cells — killing cancer cells.
Can reach cancer cells throughout the body, useful for metastatic cancer.
Side effects: also damages rapidly dividing HEALTHY cells (hair follicles, gut lining, bone marrow) — causing hair loss, nausea, immune suppression.
⚠️ Common Mistake
BENIGN tumours stay in one place and are not cancer. MALIGNANT tumours spread (metastasis) and are cancer. Students often use 'tumour' and 'cancer' interchangeably — a benign tumour is NOT cancer. Also: chemotherapy targets ALL rapidly dividing cells, not just cancer cells — that's why it causes hair loss and immune suppression as side effects.
📌 Key Note
Cancer = uncontrolled cell division caused by mutations in regulatory genes. Benign = stays put, not cancerous. Malignant = spreads via blood/lymph (metastasis) = cancer. Treatments: surgery, radiotherapy (gamma rays), chemotherapy (drugs).
🎯 Matching Activity — Benign or Malignant?
Sort each description into benign tumour or malignant tumour. — drag the symbols on the right to match the component names on the left.
Benign tumour
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Malignant tumour
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Benign tumour
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Malignant tumour
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Both
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Much harder to treat once it has spread to other organs
Grows in one place — stays enclosed, does not invade surrounding tissues
Cells break away and travel through blood or lymph to form new tumours — metastasis
Caused by uncontrolled cell division due to gene mutation
Usually not life-threatening — often removed by surgery
🎯 Test Yourself
Question 1 of 3
1. What is the key difference between a benign and a malignant tumour?
2. How does UV radiation cause skin cancer?
3. Why does chemotherapy cause hair loss as a side effect?
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