Lung cancer is cancer that forms in tissues of the lung,
usually in the cells lining air passages. The two main types are small
cell lung cancer and non-small cell lung cancer.
These types are diagnosed based on how the cells look under a microscope.
Each type of lung cancer grows and spreads in different ways and is treated
Non-small cell lung cancer. This is more common
than small cell lung cancer, and generally grows and spreads more slowly.
There are three main types of non-small cell lung cancer, named for
the type of cells in which the cancer develops: squamous cell carcinoma (also called epidermoid carcinoma), adenocarcinoma, and large
Small cell lung cancer. This is sometimes called
oat cell cancer, and is less common than non-small cell lung cancer.
Small cell lung cancer grows more quickly and is more likely to spread
to other organs in the body.
The lungs, a pair of sponge-like,
cone-shaped organs, are part of the respiratory
system. The right lung has three sections, called lobes; it is a little
larger than the left lung, which has two lobes. When we breathe in, the
lungs take in oxygen, which our cells need to live and carry out their normal
functions. When we breathe out, the lungs get rid of carbon dioxide, which
is a waste product of the body's cells.
Who is at risk?
Researchers have discovered several causes of lung cancer – most related
to the use of tobacco.
Cigarettes. Smoking cigarettes causes lung cancer.
Harmful substances, called carcinogens, in tobacco damage the cells
in the lungs. Over time, the damaged cells may become cancerous. The
likelihood that a smoker will develop lung cancer is affected by the
age at which smoking began, how long the person has smoked, the number
of cigarettes smoked per day, and how deeply the smoker inhales. Stopping
smoking greatly reduces a person's risk for developing lung cancer.
Cigars and pipes. Cigar and pipe smokers have a higher
risk of lung cancer than nonsmokers. The number of years a person smokes,
the number of pipes or cigars smoked per day, and how deeply the person
inhales all affect the risk of developing lung cancer. Even cigar and
pipe smokers who do not inhale are at increased risk for lung, mouth,
and other types of cancer.
Environmental tobacco smoke. The chance of developing
lung cancer is increased by exposure to environmental tobacco smoke
(ETS) – the smoke in the air when someone else smokes. Exposure
to ETS, or secondhand smoke, is called involuntary or passive smoking.
Radon. Radon is an
invisible, odorless, and tasteless radioactive gas that occurs naturally
in soil and rocks. It can cause damage to the lungs that may lead to
lung cancer. People who work in mines may be exposed to radon and, in
some parts of the country, radon is found in houses. Smoking increases
the risk of lung cancer even more for those already at risk because
of exposure to radon. A kit available at most hardware stores allows
homeowners to measure radon levels in their homes. The home radon test
is relatively easy to use and inexpensive. Once a radon problem is corrected,
the hazard is gone for good.
Asbestos. Asbestos is the name of a group of minerals that occur naturally as fibers and
are used in certain industries. Asbestos fibers tend to break easily
into particles that can float in the air and stick to clothes. When
the particles are inhaled, they can lodge in the lungs, damaging cells
and increasing the risk for lung cancer. Studies have shown that workers
who have been exposed to large amounts of asbestos have a risk of developing
lung cancer that is 3 to 4 times greater than that for workers who have
not been exposed to asbestos. This exposure has been observed in such
industries as shipbuilding, asbestos mining and manufacturing, insulation
work, and brake repair. The risk of lung cancer is even higher among
asbestos workers who also smoke. Asbestos workers should use the protective equipment provided by their employers and follow recommended work practices and safety procedures. Anyone who contracted mesothelioma from asbestos exposure should contact an experienced attorney immediately.
Pollution. Researchers have found a link between
lung cancer and exposure to certain air pollutants, such as by-products
of the combustion of diesel and other fossil fuels. However, this relationship
has not been clearly defined, and more research is being done.
Lung diseases. Certain lung diseases, such as tuberculosis (TB), increase a person's chance of developing lung cancer. Lung cancer
tends to develop in areas of the lung that are scarred from TB.
Personal history. A person who has had lung cancer
once is more likely to develop a second lung cancer compared with a
person who has never had lung cancer. Quitting smoking after lung cancer
is diagnosed may prevent the development of a second lung cancer.
Researchers continue to study the causes of lung cancer and to search for
ways to prevent it. We already know that the best way to prevent lung cancer
is to quit (or never start) smoking. The sooner a person quits smoking the
better. Even if you have been smoking for many years, it's never too late
to benefit from quitting.
Signs and symptoms
Common signs and symptoms of lung cancer include:
A cough that doesn't go away and gets worse over time
Constant chest pain
Coughing up blood
Shortness of breath, wheezing, or hoarseness
Repeated problems with pneumonia or bronchitis
Swelling of the neck and face
Loss of appetite or weight loss
These symptoms may be caused by lung cancer or by other conditions. It is
important to check with a doctor.
To help find the cause of symptoms, the doctor evaluates a person's medical
history, smoking history, exposure to environmental and occupational substances,
and family history of cancer. The doctor also performs a physical exam and
may order a chest X-ray and other tests.
If lung cancer is suspected, sputum cytology (the microscopic examination
of cells obtained from a deep-cough sample of mucus in the lungs) is a simple
test that may be useful in detecting lung cancer. To confirm the presence
of lung cancer, the doctor must examine tissue from the lung. A biopsy – the removal of a small sample of tissue for examination under a
microscope by a pathologist – can show whether a person has cancer.
A number of procedures may be used to obtain this tissue:
The doctor puts a bronchoscope (a thin, lighted tube) into the mouth
or nose and down through the windpipe to look into the breathing passages.
Through this tube, the doctor can collect cells or small samples of
Needle aspiration. A needle is inserted through the
chest into the tumor to remove a sample of tissue.
Using a needle, the doctor removes a sample of the fluid that surrounds
the lungs to check for cancer cells.
Thoracotomy. Surgery to open the chest is sometimes
needed to diagnose lung cancer. This procedure is a major operation
performed in a hospital.
If the diagnosis is cancer, the doctor will want to learn the stage (or
extent) of the disease. Staging is done to find out whether the cancer has
spread and, if so, to what parts of the body. Lung cancer often spreads
to the brain or bones. Knowing the stage of the disease helps the doctor
plan treatment. Some tests used to determine whether the cancer has spread
CAT (or CT)
scan (computed tomography). A computer linked to an X-ray
machine creates a series of detailed pictures of areas inside the body.
resonance imaging). A powerful magnet linked to a computer
makes detailed pictures of areas inside the body.
Scanning can show whether cancer has spread to other organs, such as
the liver. The patient swallows or receives an injection of a mildly
radioactive substance. A machine (scanner) measures and records the
level of radioactivity in certain organs to reveal abnormal areas.
Bone scan. A bone
scan, one type of radionuclide scanning, can show whether cancer has
spread to the bones. A small amount of radioactive substance is injected
into a vein. It travels through the bloodstream and collects in areas
of abnormal bone growth. An instrument called a scanner measures the
radioactivity levels in these areas and records them on X-ray film.
Mediastinoscopy/mediastinotomy. A mediastinoscopy
can help show whether the cancer has spread to the lymph nodes in the
chest. Using a lighted viewing instrument, called a scope, the doctor
examines the center of the chest (mediastinum) and nearby lymph nodes.
In mediastinoscopy, the scope is inserted through a small incision in
the neck; in mediastinotomy, the incision is made in the chest. In either
procedure, the scope is also used to remove a tissue sample. The patient
receives a general anesthetic.
Read about how lung cancer is