Cancer

A reliable Paper 1 topic. The "evidence of malignancy" question pattern. The benign-vs-malignant distinction. And why "tumour" and "cancer" are NOT the same word.

SPEC 4.2.2.7 • NON-COMMUNICABLE DISEASES

The Malignancy Evidence Trap

A recurring pattern on Paper 1 shows a body diagram with several tumour locations marked and asks: "What evidence in the diagram suggests the tumour in the lung is malignant?"

Most students write "it's in the lung" or "it's big" — and score zero. The mark-scheme answer is almost always about spread: tumours visible in more than one organ means the cancer has metastasised — and that's what makes it malignant, not the location or size. — pattern recurring across AQA cancer questions

What You Get From This Lesson

The exact definition of cancer AQA wants. The benign-vs-malignant distinction. The mechanism behind tumour formation. The difference between primary and secondary tumours. The risk factors. And how to answer the recurring "evidence of malignancy" question.

What You'll Learn

By the end of this lesson, you'll be able to:

Lesson Objectives

Describe cancer as the result of changes in cells leading to uncontrolled growth and division.

Distinguish benign from malignant tumours — and explain why only malignant tumours are cancers.

Explain how malignant cells spread through the blood to form secondary tumours.

Identify the lifestyle and genetic risk factors for cancer.

Spec ref: 4.2.2.7 (Cancer). Paper 1, Higher tier.

What Cancer Actually Is

Cancer

The result of changes in cells that lead to uncontrolled growth and division. (Spec wording — memorise verbatim.)

Breaking This Down

"Changes in cells" — usually mutations in DNA caused by environmental factors (carcinogens, radiation) or inherited from parents.

"Uncontrolled" — normally, cells only divide when needed (controlled by cell cycle checkpoints). Cancer cells ignore these controls.

"Growth and division" — cancer cells keep dividing endlessly, forming a mass of cells = a tumour.

Mark-Scheme Wording

AQA mark schemes are strict on the word "uncontrolled". Writing just "cells divide" scores zero — cells dividing is normal. The KEY word is uncontrolled. Lock this in.

Benign Tumours

Benign Tumour

A growth of abnormal cells that are contained in one area, usually within a membrane. Benign tumours do not invade other parts of the body. (Spec wording.)

Key Features

Contained — all the abnormal cells stay together in one location.

Within a membrane — a layer of tissue surrounds the tumour, keeping it isolated.

Do NOT invade neighbouring tissues.

Do NOT spread via the blood to other parts of the body.

Critical Distinction

A benign tumour is NOT cancer. The spec is clear: only malignant tumour cells are cancers. Writing "benign cancer" scores zero — it's a contradiction. Use "benign tumour" or "non-cancerous growth".

Are Benign Tumours Harmless?

Not entirely — large benign tumours can still cause problems by pressing on surrounding tissues or organs (e.g. a benign brain tumour pressing on nearby brain tissue). But they don't spread, which is the key spec distinction.

Malignant Tumours

Malignant Tumour

A tumour whose cells invade neighbouring tissues and spread to different parts of the body in the blood, where they form secondary tumours. Malignant tumours are cancers. (Spec wording.)

Three Critical Features (Spec Wording)

Invade neighbouring tissues — cells push into and damage surrounding tissue.

Spread in the blood — cells break off and enter the bloodstream.

Form secondary tumours — these cells settle in distant body parts and grow into new tumours.

Mark-Scheme Exact Phrase

The spec says cells spread "in the blood". AQA mark schemes accept this OR "bloodstream". Writing "they travel through the body" is too vague — name the blood specifically.

Benign vs Malignant — Side By Side

FeatureBenignMalignant

Contained?Yes — within a membraneNo — invades neighbouring tissues

Spreads?NoYes — spreads in the blood

Secondary tumours?NoYes — forms in distant body parts

Is it cancer?NoYes

How Cancer Develops

The "changes in cells" the spec mentions are mutations — changes in DNA. Here's the sequence:

The 4-Stage Process

DNA damage — caused by carcinogens, ionising radiation, viruses, or random errors during DNA replication.

Mutation — the damaged DNA changes the cell's instructions, especially those controlling cell division.

Uncontrolled cell division — the cell loses its checkpoints and divides repeatedly.

Tumour forms — a mass of these abnormal cells builds up.

From Tumour to Cancer

If the tumour stays contained → it's benign. If the cells gain further mutations that let them break through tissue boundaries and enter the bloodstream → it becomes malignant = cancer.

"Cell" vs "Cells"

Cancer starts from a single cell that has mutated. That one cell divides repeatedly to form a tumour. AQA can ask about this — say "a cell" or "single cell" mutates, not "cells mutate".

Primary vs Secondary Tumours

Two Key Terms

Primary tumour — where the cancer originally formed. E.g. a primary lung cancer started in the lung.

Secondary tumour (metastasis) — formed when cancer cells break off the primary tumour, enter the blood, travel to distant organs, and grow into new tumours there.

Why It Matters Diagnostically

A "lung tumour" could be: (a) a primary lung cancer, OR (b) a secondary tumour from a cancer that started elsewhere (e.g. breast cancer that spread to the lungs). Doctors test the cells to find out — secondary lung tumours often have features of the original cancer's tissue.

Evidence of Malignancy

If a diagram shows tumours of the same type in multiple organs, the evidence is that the cancer has spread / formed secondary tumours — which is the spec definition of malignant. This is the canonical 1-mark answer.

Lifestyle Risk Factors for Cancer

The spec says: "Scientists have identified lifestyle risk factors for various types of cancer." The named factors:

Risk factorType(s) of cancer

SmokingLung cancer (also mouth, throat, bladder cancers)

Carcinogens generallyVarious cancers (any substance that causes cancer)

Ionising radiationVarious cancers — including skin cancer (UV) and leukaemia (X-rays, gamma rays, radioactive sources)

Some virusesSome cancers. Spec 4.2.2.5: "Viruses living in cells can be the trigger for cancers." Viruses can disrupt the normal control of cell division when they enter host cells.

UV Radiation

UV from sunlight is a form of ionising radiation that damages DNA in skin cells — increasing the risk of skin cancer. Sunbeds also produce UV. This is examinable.

Genetic Risk Factors

Spec Wording

"There are also genetic risk factors for some cancers."

What This Means

Some people inherit specific mutations in their DNA from their parents.

These inherited mutations make their cells more likely to develop into cancer cells.

Having a genetic risk factor doesn't guarantee cancer — it just increases the probability.

Examples include certain inherited mutations linked to higher risk of breast, ovarian, and bowel cancers.

Lifestyle vs Genetic

Questions sometimes test the distinction:

Lifestyle risk factors — things you do / are exposed to (smoking, UV, diet)

Genetic risk factors — inherited from parents in your DNA

Many cancers result from both — a person may have a genetic predisposition AND a lifestyle factor that triggers it.

Carcinogens — The Mechanism

Carcinogen

Any substance or form of radiation that can cause cancer. Examples: chemicals in tobacco tar, ionising radiation, UV light, asbestos, some viruses.

How Carcinogens Cause Cancer

Carcinogen enters or contacts cells (e.g. tar from cigarette smoke reaches lung cells).

Carcinogen damages DNA in the cells.

DNA damage causes a mutation.

The mutation affects genes controlling cell division — leading to uncontrolled division.

A tumour forms; if it spreads, it's cancer.

Smoking Specifically

Tobacco smoke contains many carcinogens, found in the tar that coats the lining of the lungs. These chemicals damage DNA in lung cells, causing mutations that can lead to lung cancer. This is the mark-scheme mechanism — memorise the chain: tar → carcinogens → DNA damage → mutations → uncontrolled division → tumour.

Worked Example 1 — Evidence of Malignancy

A diagram shows a patient with one tumour in the lung, one in the liver, and one in the kidney. The doctor says all three tumours are the same type of cell.

(a) What evidence in the diagram suggests the tumour in the lung is malignant? 1 mark

(b) Describe what happens to cells when a tumour forms. 1 mark

PART A

Model answer: "The cancer has spread to other organs (liver and kidney) and formed secondary tumours. Cells from the primary tumour in the lung have entered the blood and travelled to other parts of the body." ✓

PART B

Model answer: "Cells undergo uncontrolled growth and division, producing a mass of abnormal cells (a tumour)." ✓

Part (a): identifies spread / secondary tumours — the spec definition of malignant. Mentions blood (spec word). Part (b): uses "uncontrolled" (spec word) and refers to growth and division. Common wrong answers: "tumour is big" or "tumour is in the lung" — neither demonstrates malignancy. The defining feature is SPREAD.

Worked Example 2 — Mechanism Question

Explain how smoking can lead to lung cancer. 4 marks

POINT

"Explain how" wants a mechanism: link smoking → cancer step by step using named processes.

EVIDENCE

4 marks = 4 mark-scheme points. Aim for: carcinogens / DNA damage / mutation / uncontrolled division.

EXPLAIN

Model answer:

Tobacco smoke contains carcinogens (e.g. in tar). ✓

Carcinogens damage DNA in lung cells. ✓

This causes mutations in genes that control cell division. ✓

Cells then undergo uncontrolled growth and division, forming a tumour. If malignant, this is lung cancer. ✓

4 distinct points using spec vocabulary: carcinogens → DNA damage → mutation → uncontrolled division. Each linked with "this causes" / "leading to" so the chain is explicit. Vague answers like "smoking damages the lungs" don't name a process and cap at 1-2 marks.

Three Examiner Alerts

Alert 1 — Tumour ≠ Cancer

Only malignant tumour cells are cancers. Benign tumours are NOT cancers. Writing "benign cancer" is a contradiction. Writing "cancer is a type of tumour" reverses the relationship — cancer is a specific type of MALIGNANT tumour.

Alert 2 — The Word "Uncontrolled" is Mandatory

Mark schemes require "uncontrolled" (or equivalent like "abnormal rate of") growth/division. Just "cells divide" describes a normal process. The defining cancer feature is the LOSS of control — name it specifically.

Alert 3 — "In the Blood", Not "Around the Body"

The spec says malignant cells spread "in the blood". Vague phrases like "around the body", "to other places", or "through the body" don't name the transport route. Always say blood (or bloodstream).

Common Errors — Wrong vs Right

Wrong

"Tumours are cancers."

Right

"Malignant tumours are cancers. Benign tumours are not."

Wrong

"Cancer is when cells divide too much."

Right

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

Wrong

"The cancer spread around the body."

Right

"Cells from the malignant tumour entered the blood and spread to other parts of the body, forming secondary tumours."

Wrong

"The tumour is big, so it must be malignant."

Right

"The tumour cells have spread to other organs and formed secondary tumours — this is evidence the tumour is malignant."

Wrong

"Smoking causes lung cancer."

Right

"Tobacco smoke contains carcinogens that damage DNA, causing mutations that lead to uncontrolled cell division in lung cells."

Wrong

"All cancer is caused by lifestyle."

Right

"Cancer has both lifestyle risk factors (smoking, UV, alcohol) and genetic risk factors (inherited mutations) — many cancers result from interaction of both."

Three Things To Remember

1. The Spec Definition

Cancer is the result of changes in cells (mutations) that lead to uncontrolled growth and division. The word "uncontrolled" is mandatory in mark schemes — without it, your answer doesn't describe what makes a cell cancerous.

2. Benign vs Malignant

Benign: abnormal cells contained in one area, within a membrane, do NOT invade or spread. NOT cancer.

Malignant: invade neighbouring tissues, spread via the blood, form secondary tumours in distant parts of the body. ARE cancer.

3. Risk Factors — Lifestyle AND Genetic

Lifestyle: smoking, UV/ionising radiation, alcohol, some viruses, other carcinogens. Genetic: inherited mutations make some cells more likely to develop into cancer cells. Many cancers result from interaction of both.

The Killer Question Pattern

"What evidence in the diagram suggests the tumour is malignant?" → answer is almost always "the cancer has spread / formed secondary tumours in other organs". Not size, not location — SPREAD.

Module 2 — Complete

Module 2 Covered (Spec 4.2)

2.06: Heart, blood vessels, blood (4.2.2.2, 4.2.2.3)

2.07: CHD & health issues (4.2.2.4, 4.2.2.5)

2.08: Plant tissues, transpiration, translocation (4.2.3.1, 4.2.3.2)

2.09: Lifestyle risk factors & data interpretation (4.2.2.5, 4.2.2.6)

2.10: Cancer (4.2.2.7) — this lesson

Next: Module 3 — Infection and Response

From non-communicable diseases (cancer, CHD) to communicable diseases caused by pathogens. Bacteria, viruses, fungi, protists — how they spread, how the body defends itself, vaccines, antibiotics, and drug discovery. Spec 4.3, Paper 1.

Quick Self-Check

What is cancer? (Result of changes in cells leading to uncontrolled growth and division.)

Difference between benign and malignant? (Benign = contained, doesn't spread. Malignant = invades + spreads in blood = cancer.)

What's a secondary tumour? (A new tumour formed when cells from the primary tumour spread via blood to a different part of the body.)

Name 2 lifestyle risk factors for cancer. (Smoking, UV/ionising radiation, alcohol, viruses, other carcinogens.)

What evidence shows a tumour is malignant? (It has spread / formed secondary tumours in other organs.)