Cancer and carcinogens
Cancer
Cells grow then divide by mitosis only when we need new ones – when we’re growing or need to replace old or damaged cells.
When a cell becomes A disease caused by normal cells changing so that they grow and divide in an uncontrolled way. The uncontrolled growth causes a lump called a tumour to form., it begins to grow and divide uncontrollably. New cells are produced – even if the body does not need them.
A group of cancerous cells produces a growth called a The lump of cells formed as a result of uncontrolled cell division..
Types of tumour
There are two types of tumour - A tumour that is slow-growing and non-invasive, and is therefore not cancerous. and A fast-growing tumour that is cancerous and can invade and spread to other areas of the body.. The table shows the difference between the two types:
| Type of tumour | Characteristics |
| Benign | Grows slowly; usually grow within a membrane, so can easily be removed; does not invade other parts of the body |
| Malignant | Grows quickly; invades neighbouring tissues and can spread to other parts of the body in the bloodstream; as the tumour grows, cancer cells detach and can form secondary tumours in other parts of the body - this is called metastasis. |
| Type of tumour | Benign |
|---|---|
| Characteristics | Grows slowly; usually grow within a membrane, so can easily be removed; does not invade other parts of the body |
| Type of tumour | Malignant |
|---|---|
| Characteristics | Grows quickly; invades neighbouring tissues and can spread to other parts of the body in the bloodstream; as the tumour grows, cancer cells detach and can form secondary tumours in other parts of the body - this is called metastasis. |
The diagram shows how cancer cells can invade surrounding tissue:
Cancer cells are undifferentiated – they do not carry out their normal function.
At some point, secondary tumours may develop.
Image caption, Development of a tumour
1 of 5
What causes cancer?
There are genetic factors that increase the likelihood of developing some cancers.
Chemicals and other agents that can cause cancer are called A chemical or other agent that causes cancer..
Carcinogens cause cancer by damaging Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being.. Carcinogens cause A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes. to occur. A single mutation will not cause cancer – several are required. For this reason, we are more likely to develop cancer as we get older.
Something that increases the likelihood of developing a disease is called a risk factor. There are several risk factors for various types of cancers including:
Lifestyle factors:
- viruses linked with cancer, such as the human papilloma virus (HPV), being spread from person to person through sexual intercourse
- the chemical carcinogens in cigarette smoke increasing the risk of lung cancer
- alcohol intake is linked with certain cancers
- exposure to A high energy part of the electromagnetic spectrum associated with sunburn and skin cancer. radiation, part of which is Radiation that is able to remove electrons from atoms or molecules to produce positively charged particles called ions., during sunbathing or outdoor activities, leading to the development of skin cancers
- diet, including fat and salt intake, increases the risk of cancer
Industrial and environmental factors at work:
- exposure to ionising radiation increases the risk factor
- exposure to chemical carcinogens
There are also genetic risk factors for some cancers.
