A group of researchers investigated the link between exposure to certain chemicals and the development of cancer in factory workers. Some workers developed tumours that were classified as benign, whilst others developed malignant tumours. Describe the differences between benign and malignant tumours, and explain why malignant tumours are more dangerous to health.

OCR A-Level Biology B — Advancing Biology (H422) — 3.2 Disease, mutation and cancer · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Factory workers exposed to mutagenic chemicals over many years were found to have higher rates of tumour development than the general population. Medical examination revealed that some workers had benign tumours whilst others had malignant tumours.

Model answer (5 marks)

Benign tumours are usually well‑defined, grow slowly and do not invade surrounding tissue – they stay in one place and are contained within a capsule. Malignant tumours are characterised by rapid growth, invasion of neighbouring tissues and the ability to break away from the primary site. Malignant cells can enter the bloodstream or lymphatic system and travel to other organs, where they form secondary tumours (metastases). Because metastases can affect multiple organs, malignant tumours are harder to treat and are more life‑threatening.

Examiner tips

  • Use the exact terms ‘benign’, ‘malignant’, ‘invasive’, ‘metastasis’, ‘secondary tumour’
  • Show the link between invasion and spread to explain why malignant tumours are more dangerous
  • Keep the answer concise – 5 marks, so one or two sentences per point

Common mistakes

  • Confusing ‘benign’ with ‘slow‑growing’ only – forget that benign tumours do not invade or metastasise
  • Using vague words like ‘bad’ or ‘dangerous’ without explaining the mechanism of spread
  • Omitting the term ‘metastasis’ or the idea of secondary tumours

Mark scheme (5 marks)

  1. Benign tumours do not invade surrounding tissue / stay in one place / are contained
  2. Malignant tumours invade and destroy surrounding tissue / spread into neighbouring tissues
  3. Malignant tumour cells can break away from the original tumour and travel through the bloodstream / lymphatic system
  4. Malignant cells form secondary tumours (metastases) in other parts of the body
  5. This makes malignant tumours harder to treat / more life-threatening because multiple organs can be affected

Key terms in this question

malignant tumour

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