Cancer — Benign and Malignant Tumours

Cancer is a non-communicable disease caused by uncontrolled cell division. In this lesson you will learn how normal cell division is regulated, what happens when it goes wrong, the difference between benign and malignant tumours, and the risk factors for cancer, as required by the AQA GCSE Combined Science Trilogy specification (8464).

---

Normal Cell Division

Cells in the body divide by mitosis to produce new cells for:

• Growth — increasing the number of cells in a developing organism
• Repair — replacing damaged or worn-out cells
• Replacement — maintaining tissues (e.g. skin cells are constantly replaced)

Under normal circumstances, cell division is tightly controlled. Cells only divide when they receive the correct signals, and damaged or old cells are programmed to die (a process called apoptosis).

---

What Is Cancer?

Cancer occurs when the normal control of cell division breaks down. Cells begin to divide uncontrollably, forming a mass of abnormal cells called a tumour.

This happens because of changes (mutations) in the genes that control cell division. These mutations can be caused by:

• Inherited genetic factors — mutations passed from parents
• Environmental factors (carcinogens) — substances or agents that cause mutations

---

Benign vs Malignant Tumours

There are two types of tumour:

Feature	Benign Tumour	Malignant Tumour
Growth rate	Usually slow	Often rapid
Invasion	Does NOT invade surrounding tissues	Invades and destroys surrounding tissues
Spread (metastasis)	Does NOT spread to other parts of the body	CAN spread to other parts of the body via the blood or lymphatic system (metastasis)
Capsule	Usually enclosed in a membrane/capsule	Not enclosed — grows into surrounding tissue
Danger	Usually not life-threatening (unless pressing on a vital organ)	Can be life-threatening — especially if it spreads
Example	Fibroid (uterus), lipoma (fatty tissue)	Lung cancer, breast cancer, leukaemia

graph TD
    A["Normal cell division (controlled)"] -->|"Mutation in genes controlling cell division"| B["Uncontrolled cell division"]
    B --> C{"Type of tumour?"}
    C -->|"Cells stay in one place"| D["Benign tumour"]
    C -->|"Cells invade other tissues and may spread"| E["Malignant tumour (cancer)"]
    E -->|"Cells break off and travel via blood/lymph"| F["Secondary tumours in other organs (metastasis)"]

Exam Tip: The key difference is invasion and spread. Benign tumours stay in one place and do not spread; malignant tumours can invade surrounding tissues and metastasise (spread) to form secondary tumours elsewhere in the body. Always use the term metastasis when describing how cancer spreads.

---

Risk Factors for Cancer

A risk factor is something that increases the likelihood of developing a disease. Risk factors for cancer include both lifestyle and genetic factors.

Lifestyle (Environmental) Risk Factors

Risk Factor	Type(s) of Cancer	Explanation
Smoking	Lung, throat, mouth, bladder	Tobacco smoke contains many carcinogens (cancer-causing chemicals) that damage DNA
Excessive UV radiation (sunlight or sunbeds)	Skin cancer (melanoma)	UV radiation causes mutations in skin cell DNA
Obesity	Bowel, breast, kidney, liver	Excess body fat affects hormone levels and inflammation, promoting cell division
Excessive alcohol	Liver, mouth, throat, breast	Alcohol is broken down into acetaldehyde, a carcinogen that damages DNA
Ionising radiation (e.g. X-rays, gamma rays)	Various	High-energy radiation can directly damage DNA, causing mutations
Certain viral infections	Cervical cancer (HPV), liver cancer (hepatitis B/C)	Some viruses insert their DNA into host cells, disrupting normal cell division

Genetic Risk Factors

• Some people inherit faulty genes that increase their risk of developing certain cancers
• For example, mutations in the BRCA1 and BRCA2 genes significantly increase the risk of breast and ovarian cancer
• Having a family history of a particular cancer may increase an individual's risk
• However, inheriting a cancer gene does NOT mean a person will definitely get cancer — it increases the probability

Exam Tip: Remember that risk factors increase the likelihood of cancer but do not guarantee it. Use the word "correlation" when discussing links between risk factors and cancer. Also remember that some cancers have no clear risk factor — they can occur due to random mutations during DNA replication.

---

Cancer Treatment

Treatment	How It Works	Limitations
Surgery	Physically removing the tumour	Only works if the tumour has not spread; may not remove every cancer cell
Chemotherapy	Drugs that kill rapidly dividing cells	Also kills normal rapidly dividing cells (e.g. hair follicles, bone marrow), causing side effects like hair loss and weakened immunity
Radiotherapy	High-energy radiation targeted at the tumour to destroy cancer cells	Can damage surrounding healthy tissue; may cause side effects

Exam Tip: Chemotherapy does not specifically target cancer cells — it targets all rapidly dividing cells. This is why it causes side effects like hair loss (hair follicle cells divide rapidly) and nausea (gut lining cells divide rapidly).

---

Interaction Between Communicable and Non-Communicable Disease

The AQA specification requires you to understand that communicable and non-communicable diseases can interact:

Interaction	Example
A viral infection can trigger cancer	Human papillomavirus (HPV) can cause cervical cancer
Immune system deficiency increases infection risk	Cancer treatment (chemotherapy) weakens the immune system, increasing the risk of communicable diseases
A disease can lead to poor mental health	A cancer diagnosis can cause depression and anxiety
Poor physical health can reduce the ability to fight infection	Malnutrition due to cancer can weaken the immune response

---

Common Mistakes