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What is cancer?
All living things -
ourselves included - are made up of
cells. Cells are microscopic packages of
living material and we have billions of
them. They come in many different types:
liver cells, brain cells, blood cells and
so on. In the normal adult, cells only
grow and divide slowly and under very
tight control to make sure that the
number of cells in each tissue stays the
same. Cancer begins when one cells
changes and starts growing and dividing
rapidly and out of control. This one
cells divides to give two cells, then
four, eight and so on until they form
growing mass of cancer cells -
called a tumour.
What do malignant
and benign mean?
In some tumours, the cells
stay in the same place and as the tumour
stops growing before it gets very
large - often because it simply runs
out space to grow. These are called
benign tumours and they are not normally
dangerous. We all have benign tumours,
such as moles and warts. However, in
other tumours the cells are able to
invade the surrounding tissue and spread
into nearby organs where they can cause
serious and, eventually, fatal damage.
These are called malignant tumours.
What is
metastasis?
In many malignant tumours,
as the cells spread, they come across
blood vessels. If they actually spread
into the blood vessel, they get carried
around the body and eventually get stuck
in a smaller blood vessel in another part
of the body. Here they begin to divide
and grow again eventually forming a new
tumour. These are called secondary
tumours or metastases. This process of
cancers spreading around the body is
called metastasis.
Do genes cause
cancer?
Every cell carries a set
of coded instructions for every activity
or function that it can perform.
Different genes are active in different
cells, which is why a brain cell carries
out many different activities from muscle
cell. Genes also carry the coded
instructions for basic functions of the
cell such as the way cells grow and
divide. The growth and division of normal
cells is tightly controlled by the
activity of certain genes. However, when
these genes are faulty or when they
mechanisms controlling the activity of
these genes is damaged, it can cause the
growth and division of the cells to go
out of control - in other words, the
become cancerous. Genes themselves do not
cause cancer. When they function
normally, genes prevent cancer. However,
it is when some genes become damaged that
they can malfunction and cause cancer.
Can you inherit
cancer?
Cancer itself cannot be
inherited, but some people do inherit a
higher risk of getting cancer. This is
because they inherit, from their parents,
a slightly damaged version of one of the
genes involved in controlling cell
division. On its own, this damaged gene
is not enough to make cells cancerous.
Normally, two or three different genes
have to be damaged before a cell will
become cancerous. That is why so very few
of the billions of cells in our body ever
become cancerous. However, if someone
starts out with every cell in their body
carrying damage in one of these genes,
the chance of a cell getting the other
types of gene damage and becoming
cancerous is much higher. Some of these
inherited damaged genes have been
identified, such as BRCA1 and BRCA2 which
increase the risk of getting breast
cancer by five to seven times.
Do tumours need a
blood supply?
A tumour usually starts
with a single cancerous cell that begins
growing and dividing. The resulting mass
of cancer cells soon gets large enough to
need a new blood supply to provide oxygen
and nutrients and to remove waste
products. Without a blood supply, the
cells in the middle of the tumour will
die off. In fact, tumours without a blood
supply are unable to grow more that about
one millimetre across. As soon as they
start growing, tumours release small,
hormone-like molecules that cause nearby
blood vessels to start growing towards
the tumour until they actually form a new
branch supplying the tumour with blood.
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