Types of tumours and carcinogens

In a nutshell

Cancers form growths known as tumours. These tumours can either be benign or malignant. Benign tumours are harmless, whereas malignant tumours spread very quickly around the body. Carcinogens cause cancer, and there is a clear correlation between certain carcinogens and cancer cases.

Cancer

Cells grow and divide by mitosis to create new cells that replace old or damaged ones. Sometimes this goes wrong and the cell divides uncontrollably. This is known as cancer. These extra cells form growths called tumours. Tumours are normally solid, apart from blood cancers like leukaemia.

Types of tumour

Benign tumours

Benign tumours divide slowly. They do not spread and are generally harmless. They often have a capsule around them that allows them to be removed easily. Sometimes they can press on other body organs and form an unsightly growth, which is why they are removed.

Example

Warts are benign tumours. They can be removed by simple surgery or a squirt of liquid nitrogen.

Malignant tumours

Malignant tumours divide very quickly. They invade nearby tissues and spread via the blood to different parts of the body. This is where they form secondary tumours.

Biology; Global challenges; KS4 Year 10; Types of tumours and carcinogens

1.	Malignant cells develop.
2.	Malignant cells divide by mitosis and invade normal tissues.
3.	Malignant cells detach from the tumour and spread to other body parts.
4.	The malignant tumour secretes hormone-like chemicals.
5.	This causes blood vessels to grow around the tumour. This allows the tumour to have its own blood supply that provides it with food and oxygen.
6.	Malignant cells can detach from the tumour and are carried in the blood.
7.	A malignant cell is able to squeeze through the capillary wall.
8.	The cell divides to produce a secondary tumour.

Carcinogens

Definition

Carcinogens are chemicals and other agents that cause cancer.

They are able to cause cancer by damaging DNA. Changes to the DNA of a cell are known as mutations, which can also occur by chance if a mistake happens during cell division. Some genes have the role of suppressing tumour growth. This is a natural check for errors during the cell cycle. If these genes are mutated, a tumour will form. Several mutations are required to trigger cancer, this is why cancer is more common in older people.

Examples of carcinogens

Viruses like HPV.
Chemicals in the home, industry or environment.
Ionising radiation.
Ultraviolet (UV) radiation.
Lifestyle choices such as alcohol and diet.

Interpreting correlation data

You may have to interpret data between causes of cancer and cancer cases/deaths.

Example

Biology; Global challenges; KS4 Year 10; Types of tumours and carcinogens — 1. The number of breast cancer deaths per $100,000$ females, 2. The intake of animal fat in grams.

Each point represents a country.

As animal fat intake increases, the breast cancer death rate per $100,000$ females also increases. Eating less than $20\ g$ of animal fat per day has no breast cancer deaths per $100,000$ females. Eating more than $160\ g$ of animal fat per day increases the breast cancer death rate to over $20$ per $100,000$ . There is a clear positive correlation between animal fat intake and deaths from breast cancer. This suggests that eating a poor diet that is high in animal fat increases your risk of dying if you have breast cancer. However, correlation does not always equal causation and further investigations should be carried out to determine how a high animal fat diet impacts cancer in the body.