This leaflet gives a short account about what is cancer, what are
tumours, and how cancers develop and spread. There are separate
leaflets on the individual types of cancer such as breast cancer,
prostate cancer, lung cancer, skin cancer, etc.
What is cancer?
Cancer is a disease of the cells in the body. There are many
different types of cell in the body, and many different types of cancer
which arise from different types of cell. What all types of cancer have
in common is that the cancer cells are abnormal and multiply 'out of
control'. However, there are often great differences between different
types of cancer. For example:
- Some grow and spread more quickly than others.
- Some are more easy to treat than others, particularly if diagnosed at an early stage.
- Some respond much better than others to chemotherapy, radiotherapy, or other treatments.
- Some have a better outlook (prognosis) than others. For some types
of cancer there is a very good chance of being cured. For some types of
cancer, the outlook is poor.
So, cancer is not just one condition. In each case it is
important to know exactly what type of cancer has developed, how large
it has become, whether it has spread, and how well the particular type
of cancer responds to various treatments. This will enable you to get
reliable information on treatment options and outlook.
What are cells?
Normal body cells
The body is made up from
millions of tiny cells. Different parts of the body such as organs,
bones, muscles, skin, and blood are made up from different specialised
cells. All cells have a centre called a nucleus. The nucleus in each
cell contains thousands of genes which are made up from a chemical
called DNA.
The genes are like 'codes' which control the
functions of the cell. For example, different genes control how the
cell makes proteins, or how and when to make hormones or other
chemicals. Certain genes control when the cell should divide and
multiply, and certain genes even control when the cell should die.
Most
types of cell in the body divide and multiply from time to time. As old
cells wear out or become damaged, new cells are formed to replace them.
Some cells normally multiply quickly. For example, you make millions of
red blood cells each day as old ones become worn out and are broken
down. Some cells do not multiply at all once they are mature, for
example, brain cells.
Normally, your body only makes the right number of cells that are needed.
Abnormal cells
Sometimes a cell becomes
abnormal. This occurs because one or more of the genes in the cell has
become damaged or altered. The abnormal cell may then divide into two,
then four, then eight, and so on. Lots of abnormal cells may then
develop from the original abnormal cell. These cells do not know when
to stop multiplying. A group of abnormal cells may then form. If this
group of cells gets bigger, it becomes a large clump of abnormal cells
called a tumour.
What are tumours?
A tumour is a 'lump' or 'growth' of tissue made up
from abnormal cells. Tumours are divided into two types - benign and
malignant.
Benign tumours
These may form in various
parts of the body. Benign tumours grow slowly, and do not spread or
invade other tissues. They are not 'cancerous' and are not usually
life-threatening. They often do no harm if they are left alone.
However, some benign tumours can cause problems. For example, some grow
quite large and may cause local pressure symptoms, or look unsightly.
Also, some benign tumours that arise from cells in hormone glands can
make too much hormone which can cause unwanted effects.
Malignant tumours ('cancers')
Malignant
tumours tend to grow quite quickly, and invade into nearby tissues and
organs which can cause damage. The original site where a tumour first
develops is called a primary tumour. Malignant tumours may also spread
to other parts of the body to form 'secondary' tumours (metastases).
These secondary tumours may then grow, invade and damage nearby
tissues, and spread again. Note: not all cancers form solid tumours.
For example, in cancer of the blood cells (leukaemia) many abnormal
blood cells are made in the bone marrow and circulate in the
bloodstream.
How do malignant tumours grow and spread?
