Download What is cancer

What is cancer
Cancer is a disease caused by normal cells changing so that they grow in an uncontrolled
way. The uncontrolled growth causes a lump called a tumour to form. If not treated, the
tumour can cause problems by spreading into normal tissues nearby or by causing
pressure on other body structures. This is all explained more fully below.
There are over 200 different types of cancer because there are over 200 different types of
body cells. For example, cells that make up the lungs can cause a lung cancer. There are
different cells in the lungs, so these may cause different types of lung cancer
Cancer may begin as a single, genetically abnormal cell. As this one cell divides, it
eventually becomes a tumor and develops a blood supply to nourish its continued growth.
At some point, cells may break off from the primary mass and move to other parts of the
body and could cause other types of cancer.
Normal Cells
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Genes and Cancer
Different types of cells in the body do
different jobs, but they are basically
similar. They all have a centre called a
nucleus. Inside the nucleus are the genes.
Genes are really bits of code. The
information they carry can be switched on
or off. The genes control the cell. They
decide when it will reproduce, what it does
and even when it will die.
normal cell
Normally the genes make sure that cells
grow and reproduce in an orderly and
controlled way. If the system goes wrong
for any reason, the usual result is that the
cell dies. Rarely, the system goes wrong in
a way that allows a cell to keep on
dividing until a lump called a 'tumour' is
formed.
Your body is made up of billions of cells
that can only be seen under a microscope.
These cells are grouped together to make
up the tissues and organs of our bodies.
They are a bit like building blocks.
Different types of body tissues are made up
of different types of body cells. For
example, there are bone cells in bone and
breast cells in the breast.
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Cancer Cell Division
When it comes to cell division, cancer cells break just about all the rules!
The amount of time it takes for cell division to completely take place ranges widely,
depending on the species involved: some bacteria, for example, can complete cell
division in 20 minutes, while mammals such as humans may take 12-24 hours.
In the case of growing organisms like a fetus or a young animal, cell division takes place
rapidly because the organism cannot grow and thrive without a rapid replication of cells,
especially in the case of an embryo. Fully grown organisms divide cells on a much slower
scale, to slowly renew the body, except in areas like the skin and bone marrow, which are
constantly generating new cells. If an injury is sustained, the cells can divide more
quickly to heal the area.
However, cell division can get out of control. This rapid growth of cells is known as
cancer, and produces characteristic clusters of cells that take the form of tumors and other
growths, which can kill if left untreated. The reason for out of control cell division is
unknown, although scientists have shown that some substances can stimulate rapid cell
division. These substances, or carcinogens, are required by law in many places to be
labeled as a health risk. The mutated cells which double into cancers must also be
completely eliminated from the body for the risk to be reduced to zero, as the cells may
continue to reproduce if left alone. For this reason, many cancer treatments are very
radical, to ensure that all of the harmful cells are excised from the body to prevent a
recurrence.
Cancer cells can divide without appropriate external signals.
This is like a car moving without having pressure applied to the gas pedal. An example
would be the growth of a breast cancer cell without the need for estrogen. Usually, the
breast cells will only multiply when estrogen, a chemical sent from a gland in the brain, is
present. However, in breast cancer cells, the cells bypass the need from estrogen to begin
their division, resulting in uncontrolled growth.
Cancer cells do not exhibit contact inhibition.
While most cells can tell if they are being 'crowded' by nearby cells, cancer cells no
longer respond to this stop signal. The continued growth leads to the piling up of the cells
and the formation of a tumor mass.
Cancer cells can divide without receiving the 'all clear' signal.
While normal cells will stop division in the presence of genetic (DNA) damage, cancer
cells will continue to divide. The results of this are 'daughter' cells that contain abnormal
DNA or even abnormal numbers of chromosomes. These mutant cells are even more
abnormal than the 'parent' cell. In this manner, cancer cells can evolve to become
progressively more abnormal. In other words, these cells are passing are passing on their
“abnormal” traits to new cells in your body. As a result, more and more cells in your
body grow uncontrollably.