Cancer
Cells grow then divide by A type of cell division which produces daughter cells identical to the parent. only when we need new ones. This is 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 because they do not respond to regulatory signals. 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
Tumours are of two types called A tumour that is not cancerous and cannot spread to other areas of the body. and A fast-growing tumour that is cancerous and can invade and spread to other areas of the body.:
| Type of tumour | Characteristics |
| Benign | Grow slowly. Usually grow within a membrane, so can easily be removed. Do not invade other parts of the body. |
| Malignant | Grow quickly. Invade neighbouring tissues and can spread to other parts of the body in the bloodstream. As the tumour grows, cancer cells may fail to attach to each other, spreading through the body where they may form secondary tumours. This process is called metastasis. |
| Type of tumour | Benign |
|---|---|
| Characteristics | Grow slowly. Usually grow within a membrane, so can easily be removed. Do not invade other parts of the body. |
| Type of tumour | Malignant |
|---|---|
| Characteristics | Grow quickly. Invade neighbouring tissues and can spread to other parts of the body in the bloodstream. As the tumour grows, cancer cells may fail to attach to each other, spreading through the body where they may form secondary tumours. This process is called metastasis. |
The diagram shows how cancer cells can invade surrounding tissue:
Image caption, Growth of a malignant tumour by mitosis
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Cancer cells are undifferentiated 鈥 they do not carry out their normal function.
At some point, secondary tumours may develop.
Image caption, The spread of a tumour by metastasis
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