Cancer
Cancer is the general name for a
group of more than 100 diseases. Although there are many kinds of cancer, all
cancers start because abnormal cells grow out of control. Untreated cancers can
cause serious illness and death.
The body is made up of trillions of
living cells. Normal body cells grow, divide, and die in an orderly fashion.
During the early years of a person’s life, 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 starts when cells in a part
of the body start to grow out of control. Cancer cell growth is different from
normal cell growth. Instead of dying, cancer cells continue to grow and form
new, abnormal cells. Cancer cells can also invade (grow into) other tissues,
something that normal cells cannot do. Growing out of control and invading
other tissues are what makes a cell a cancer cell.
Cells become cancer cells because of
DNA (deoxyribonucleic acid) damage. DNA is in every cell and it directs all the
cell’s actions. In a normal cell, when DNA gets damaged the cell either repairs
the damage or the cell dies. In cancer cells, the damaged DNA is not repaired,
and the cell doesn’t die like it should. Instead, the cell goes on making new
cells that the body doesn’t need. These new cells all have the same abnormal
DNA as the first cell does.
People can inherit abnormal DNA, but
most DNA damage is caused by mistakes that happen while the normal cell is
reproducing or by something in the environment. Sometimes the cause of the DNA
damage may be something obvious like cigarette smoking or sun exposure. But
it’s rare to know exactly what caused any one person’s cancer.
In most cases, the cancer cells form
a tumor. Some cancers, like leukemia, rarely form tumors. Instead, these cancer
cells involve the blood and blood-forming organs and circulate through other
tissues where they grow.
Cancer cells often travel to other
parts of the body where they begin to grow and form new tumors. This happens
when the cancer cells get into the body’s bloodstream or lymph vessels. Over
time, the tumors replace normal tissue. The process of cancer spreading is
called metastasis.
No matter where a cancer may spread,
it’s always named for the place where it started. For example, breast cancer
that has spread to the liver is called metastatic breast cancer, not liver
cancer. Likewise, prostate cancer that has spread to the bone is called
metastatic prostate cancer, not bone cancer.
Different types of cancer can behave
very differently. For instance, lung cancer and skin cancer are very different
diseases. They grow at different rates and respond to different treatments.
This is why people with cancer need treatment that is aimed at their kind of
cancer.
Half of all men and one-third of all
women in the US will develop cancer during their lifetimes.
Today, millions of people are living
with cancer or have had cancer. The risk of developing many types of cancer can
be reduced by changes in a person’s lifestyle, for example, by staying away
from tobacco, limiting time in the sun, being physically active, and healthy
eating.
There are also screening tests that
can be done for some types of cancers so they can be found as early as possible
– while they are small and before they have spread. In general, the earlier a
cancer is found and treated, the better the chances are for living for many
years.
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