Lung Cancer
Signs
and symptoms
Because
lung cancer doesn't cause signs or symptoms in its earliest
stages, it's often advanced by the time it's diagnosed.
When symptoms do occur, the most common warning sign is
a cough, which occurs when a tumor irritates the lining
of the airways or blocks the passage of air. In addition
to a new cough, be alert for:
* "Smoker's cough" that worsens
* Coughing up blood, even a small amount
* Chest pain
* Shortness of breath
* New onset of wheezing
* Repeated bouts of pneumonia or bronchitis
* Hoarseness that lasts more than two weeks
Lung
cancer also may cause fatigue, loss of appetite and weight
loss. If it has spread to other parts of your body (metastasized),
you may have headaches or bone pain.
Causes
Your
lungs are two large, spongy organs shaped something like
an upside-down butterfly. One lung is located on each side
of your chest. They're separated by the mediastinum — the
tissues and organs of your midchest, which include your
heart, esophagus and windpipe (trachea) as well as lymph
nodes and major blood vessels such as the aorta. Each lung
is divided into upper sections called lobes. Your left lung
has two lobes, and your right lung, which is larger, has
three lobes.
Every
time you inhale, air is carried through the windpipe to
your lungs in two major airways (bronchi). Inside your lungs,
the bronchi subdivide over 15 times into a million smaller
airways (bronchioles), which finally end in clusters of
tiny air sacs called alveoli. Within the air sacs, oxygen
is absorbed into your bloodstream and carbon dioxide — a
waste product of metabolism — is released.
How
cancer forms
The lining of the airways and windpipe is made up of rectangular-shaped
surface cells (columnar epithelium) and glands that produce
mucus and other fluids. In healthy lungs, these cells divide
in a controlled and orderly way. But when a cell becomes
cancerous, it can continue to reproduce even when new cells
aren't needed.
Although
it may take years for lung cancer to develop, changes in
lung tissue can begin almost immediately after your lungs
are exposed to the cancer-causing substances (carcinogens)
in cigarette smoke. With repeated exposure, normal cells
are increasingly damaged, and eventually some may become
cancerous. Because of the way lung cancer cells behave and
because these cells have easy access to a large number of
blood and lymph vessels, cancerous cells may spread to other
parts of your body before you ever experience symptoms.
Leading
causes of lung cancer
Cigarette smoking is the main cause of lung cancer. Tobacco
smoke contains more than 3,500 chemicals, at least 40 of
which are known carcinogens. Cigarettes also contain more
than 30 toxic metals, including nickel and cadmium, as well
as radioactive compounds.
Other
causes of lung cancer include exposure to secondhand smoke,
to asbestos and other industrial carcinogens, and to high
concentrations of radon — an odorless gas that's released
into the air from the breakdown of uranium in the soil and
water. Smokers exposed to asbestos and radon are more likely
to develop cancer than are nonsmokers.
Lung
cancer that begins in the lungs (primary lung cancer) is
uncommon in nonsmokers, but cancer of the breast, colon,
prostate, testicle, kidney, thyroid, bone or other organs
may spread to the lungs. In that case, the cancer is still
referred to by the name of the organ in which it originated,
rather than being called lung cancer. There's no connection
between smoking and the spread of cancer cells to the lungs
from other parts of the body.
Types
of lung cancer
Lung cancer is commonly divided into two types: small cell
and non-small cell. Each grows and spreads in different
ways and is treated differently. Small cell lung cancer
spreads early in the course of the disease and occurs almost
exclusively in smokers. Surgical removal usually isn't an
option for this type of cancer; instead, it's best treated
with chemotherapy and radiation. Even so, the five-year
survival rate for small cell lung cancer is very low.
Non-small
cell lung cancer, which is more common, accounts for more
than 75 percent of lung cancers. If caught early when it's
confined to a small area, it often can be removed surgically.
There are four major categories of non-small cell lung cancer:
* Squamous cell carcinoma. This cancer forms in cells lining
your airways. It's the most common type of lung cancer in
men.
* Adenocarcinoma. This type of cancer usually begins in
the mucous-producing cells of the lung. It's the most common
type of lung cancer in women and in people who have never
smoked or were exposed to secondhand smoke.
* Large cell carcinoma. This type of cancer originates in
the peripheral part of the lungs.
* Bronchoaveolar carcinoma. This uncommon type of non-small
cell lung cancer tends to grow more slowly than other forms
of the disease. It occurs more often in smokers than in
nonsmokers and tends to arise in more than one location
at the same time.
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The information on this page has been extracted from http://www.mayoclinic.com/health/lung-cancer/DS00038/DSECTION=2
