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So what is Cancer? 2014-02-02
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Cancer is the *uncontrolled growth and spread of abnormal cells in
the body*.
The body is made up of a plethora of living cells. Normal body
cells grow, divide to make new cells, and die in an orderly
fashion. During a person's early years, these normal cells divide
faster to allow the person to grow. After the person becomes an
adult, most cells divide only to replace worn-out or dying cells,
or to repair injuries.
Cancer begins when cells in a part of the body start to grow out of
control. There are many kinds of cancer, but they all start because
of out-of-control growth of abnormal cells. These cells keep
dividing and thus creating more cells even when they are not
needed. When this happens, a mass of tissue forms. This mass of
extra tissue is called a tumor. Tumors are found in all kinds of
tissue, and can be either *benign* or *malignant*.
Benign tumors are not cancer. They usually can be removed and, in
most cases, they do not come back. Most important, cells from
benign tumors do not spread to other parts of the body. Cells from
benign tumors stay together and often they are surrounded by a
containing membrane. Benign tumors are not usually a threat to
life.
Malignant tumors are cancer. Cancer cells can invade and damage
tissues and organs near the tumor. Cancer cells also can break away
from a malignant tumor and enter the lymphatic system or the
bloodstream, which is how cancer can spread to other parts of the
body. The characteristic feature of cancer is the cell's ability to
grow rapidly, uncontrollably, and independently from the tissue
where it started.
Cells become cancer cells because of damage to DNA. Every cell
contains DNA and it directs all its actions. When DNA gets damaged
in a normal cell, the cell either repairs the damage or the cell
dies. In cancer cells, the damaged DNA is not repaired, but the
cell doesn't die like it should. Instead, this cell goes on making
new cells that the body does not need. These new cells will all
have the same damaged DNA as the first cell does.
One can inherit damaged DNA, but most DNA damage is caused by
mistakes that happen while the normal cell is reproducing or by
something in our environment. Sometimes the cause of the DNA damage
is something obvious, like cigarette smoking (which, for the
record, I do not). But more often than not no clear cause is found.
Often cancer cells travel to other parts of the body, where they
begin to grow and form new tumors replacing normal tissue. This
process of spreading is called metastasis, it happens when the
cancer cells get into the bloodstream or lymph vessels of our body.
