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Lung Cancer

What Is Lung Cancer?

Last modified: 
17/04/2013 - 13:30

Contributing Author: Guy Slowik FRCS

Lung cancer is an uncontrolled growth of abnormal cells in one or both of the lungs.

The body is made up of different types of cells that normally divide and multiply in an orderly way. These new cells replace older cells. This process of cell birth and renewal occurs constantly in the body. Abnormal cells also periodically normally appear but are removed by natural defense mechanisms.

Cancer, also known as a malignant growth, occurs when:

  • The body's natural defenses, such as certain parts of the immune and other protective systems, cannot stop the uncontrolled cell division, cancer begins.
  • These abnormal cells become greater and greater in number, and come together to form a tumor, which is a cellular growth that forms a progressively enlarging mass. Such tumors are benign unless they invade surrounding tissues and organs, in which case they are malignant.

Cancerous tumors grow out of control and can invade, replace, and destroy normal cells near the tumor. In some cases, cancer cells spread (or metastasize) to other areas of the body.

Lung cancer generally takes many years to develop even though damage to the lungs may occur shortly after a person is exposed to cancer-causing substances.

Nice To Know:

About The Lungs

The air we breathe is taken into the two lungs, situated within the chest. Inside the lungs, oxygen is extracted from the air and carbon dioxide, a waste product from the body, is breathed out. The lungs are cone-shaped and are made up of lobes. The right lung has three lobes and the left lung has two lobes.

Inside the lungs are air tubes, called bronchi. The right and left main bronchi come off the main breathing pipe, and then split up into much smaller tubes within each lung. Those, in turn, branch into thousands of very small airways called bronchioles.

The chest cavity in which the lungs sit is known as the pleural cavity. The smooth lining that surrounds and protects the lungs, enabling them to smoothly expand and contract as we breathe, is called pleura.

Different Types Of Lung Cancer

There are different types of cells in the lung, of varying size, for the different functions of the lung. This has resulted in the classification of two main types of lung cancer:

  • Cancer developing from the cells of neural origin in the lung is known as small-cell lung cancer.
  • Other types of cancers in the lung are known as non-small-cell lung cancer.
  • Some lung cancers are a mixture of both types.

The different types of lung cancers tend to grow and spread differently and are therefore not treated in the same way.

  • Non-small-cell lung cancer is the more common type, accounting for about 80% of lung cancers. It is this more common type of lung cancer that grows and spreads more slowly.
  • This less common type of cancer, small-cell cancer, is the type that grows more quickly and has a greater chance of spreading to other parts of the body.

Since the more common non-small cell group of cells in the lung are themselves made up of differing kinds of cells, three distinct types of non-small cell lung cancer are recognized. They are:

  • Squamous cell carcinoma, often found in the central part of the lung.
  • Adenocarcinoma, often occurring in the outer part of the lung.
  • Large cell carcinoma, which can occur anywhere in the lung.

People with adenocarcinoma have a more favorable outlook. However, any non-small cell cancers can begin to grow very rapidly and have an unfavorable prognosis.

In general, the choice of treatment and the chances of recovery from lung cancer following treatment will depend on the biological nature of the tumor, which, in turn, is probably related to:

  • How advanced the cancer is at the time of diagnosis
  • How healthy the person generally is

Need To Know:

Recognizing The Symptoms

Most lung cancers are discovered as a result of chest x-rays taken for routine checkups or for minor symptoms. The symptoms that may suggest lung cancer are similar to symptoms of other lung conditions that may not be as serious as lung cancer.

The main symptoms suggesting lung cancer are:

  • Coughing up blood
  • Coughing that does not seem to improve and gets worse with time

Other symptoms may include:

  • Chest pain
  • Shortness of breath
  • Recurrent episodes of pneumonia
  • Weight loss
  • Feeling tired

Weight loss and feeling tired can be symptoms of cancer in general.

Facts About Lung Cancer

  • Lung cancer is the leading cause of cancer death, causing 1.4 million deathe worldwide each year. In comparison, stomach cancer -- the second leading cause of cancer death -- causes 740,000 deaths per year.
  • Lung cancer is expected to cause 160,340 deaths in the United States in 2012.
  • 6.94% of people born today will be diagnosed with lung cancer during their lifetime.
  • More than 80% of all lung cancers are caused directly by smoking.
  • Stopping smoking can reduce the risk for developing lung cancer.
  • When initially diagnosed, only about 15% of lung cancers are still in the early stage, while 85% have already spread locally or to more distant sites in the body.
  • About half of people first diagnosed with lung cancer when the cancer is still in the early stages are alive five years later (known as the "five-year survival rate").
  • About 1%
  • In the United States, 226,160 new cases of lung cancer will be diagnosed in 2012, accounting for about 14% of cancer diagnoses.
  • $10.3 billion is spent in the United States each year on lung cancer treatment
  • About 28% of all cancer deaths in the United States are due to lung cancer.
  • About 1 in 13 men will develop lung cancer during their lifetimes, compared to about 1 in 16 women.
  • Since 1987, more women have died each year of lung cancer than breast cancer.

Sources: National Cancer Institute, World Health Organization, American Cancer Society

 

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Lung Cancer

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.