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D2.1.17 (HL)—Tumour differences

Benign tumours remain local, while malignant tumours invade tissues and can metastasize to form secondary tumours elsewhere in the body.

Syllabus
First assessment 2025
Objective
D2.1.17
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper1
Typical marks1

Common command terms

  • Suggest

Scoring notes

Common mistake
Assuming every tumour is malignant or metastatic.

Recent exam appearances

November 2024Paper1 ["HL"] · TZ05[ 1 ]D2.1.17 (HL)—Tumour differences
November 2020Paper1 ["HL"] · TZ04[ 1 ]D2.1.17 (HL)—Tumour differences
Practice this objective

Coverage 2020–2024 · Updated 16 Jul 2026

Distinguish Tumours and Measure Mitotic Index

HL only

Tumours differ in division and growth rate, invasion of neighbouring tissue and capacity for metastasis; these features determine whether they cause cancer.

Term Meaning
Benign tumour Remains localized and does not invade or metastasize; it is non-cancerous
Malignant tumour Invades neighbouring tissue and can metastasize; it is cancerous
Primary tumour Original site at which the tumour developed
Secondary tumour New tumour formed elsewhere after malignant cells spread

Metastasis occurs when cells leave a primary tumour, travel through the body and establish one or more secondary tumours.

\text{mitotic index}=\frac{\text{number of cells observed in mitosis}}{\text{total number of cells observed}}

If 24 of 200 observed tumour cells are in mitosis, the mitotic index is 24 ÷ 200 = 0.12, or 12%. Under comparable sampling conditions, a higher index indicates a larger proportion actively dividing.

Tumour size alone does not establish malignancy. Invasion and metastasis distinguish malignant cancer, while mitotic index estimates division activity only for the sampled population and time.

Tumour differences

HL only

Assessment in practice

1 marks
How it is assessed

This objective is assessed through multiple choice, commonly using Suggest.

Command terms

Suggest

What earns marks

Build the answer around this relationship: Benign tumours grow locally and do not invade distant tissues.

Watch for

Assuming every tumour is malignant or metastatic.

Representative question

Question 1

[Maximum number: 1]

Which processes occur during the development of secondary tumours?

I. Cytokinesis
II. Metastasis
III. Mitosis

A

I and II only

B

II and III only

C

I and III only

D

I, II and III

HL Cell Cycle and Cancer

HL only

Cell proliferation increases cell number by repeated mitosis, as in plant meristems, early embryos, skin replacement, and wound healing. The cell cycle includes interphase, mitosis, and cytokinesis; interphase has G1 growth, S-phase DNA replication, and G2 preparation. Interphase is metabolically active, not resting; cells synthesize proteins, replicate DNA, grow cytoplasm, and increase organelles. Cyclin concentrations rise and fall to activate cyclin-dependent kinases; CDK-cyclin complexes such as MPF control checkpoints and mitosis entry. Proto-oncogene activation and tumour suppressor loss disrupt checkpoints; accumulated mutations can cause uncontrolled proliferation and cancer. Benign tumours grow locally, malignant tumours invade neighbouring tissues, and metastasis spreads cancer cells to form secondary tumours.

Concept essentials

  • Benign tumours grow locally and do not invade distant tissues.
  • Malignant tumours can invade surrounding tissue.
  • Metastasis spreads cancer cells to form secondary tumours.
  • Secondary tumours still require cell division after cancer cells spread.