Lung Cancer Causes and Risk Factors

Quitting Smoking Greatly Reduces the Risk of Lung Cancer

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The diagnosis of lung cancer can be devastating. If it happens to you or a loved one, you'll want accurate information and answers to your questions in terms you can understand.

How Cancer Starts

All cancers form at the cellular level in our bodies. Under normal circumstances, cells grow, divide, and produce more cells to keep the body functioning properly. Sometimes though, cells keep dividing and producing when new cells are not needed.
These extra cells form a tumor, which can be either benign or malignant.
  • Benign tumors are not cancer. They are usually harmless, and when removed, rarely return. They do not spread to other parts of the body, and aren't usually life threatening.
  • Malignant tumors are cancer. The cells inside of them are abnormal and divide and grow without control. They can destroy normal tissue around the tumor, and the cells from a malignant tumor can break away and spread to other parts of the body by entering the bloodstream or the lymphatic system. This process of spreading is called metastasis, which is how cancer travels from a primary tumor to other sites within the body, creating secondary tumors.

Lung Cancer Types

Two kinds of cancer can affect the lungs: non-small cell cancer and small cell cancer. They are identified by how they look under a microscope, and are distinguishable by how they grow and spread.
Treatment programs differ, depending on which cancer a person has.

Non-small cell lung cancer is more common than small cell cancer, and tends to grow and spread more slowly than small cell cancer. This cancer is further divided into three types. They are named after the cells affected:
  • squamous cell carcinoma (also called epidermoid carcinoma)
  • adenocarcinoma
  • large cell carcinoma
Small cell lung cancer, also sometimes referred to as oat cell cancer, is less common than non-small cell cancer. It will often spread to other parts of the body, creating secondary tumors.

Cheryl's Story details one woman's courageous battle with small cell lung cancer, stage III-B.

Lung Cancer Risk Factors

Lung cancer has several causes, most revolving around tobacco use. According to the American Cancer Society, 87 percent of all lung cancers cases involve tobacco use.

Cigarette Smoking

Cigarette smoke contains numerous carcinogens, as well as other toxins. Cigarette smoke that is breathed into the lungs damages the body's cells, and over time, those cells can become cancerous.

Factors that appear to influence whether a person will develop lung cancer are:

  • age the person was when they starting smoking
  • the number of pack years they've smoked
  • how deeply the smoke was inhaled
Smoking cessation is the best choice a person can make to reduce his risk of getting lung cancer.

Cigars and Pipe Smoking

The above information about cigarette smoking applies to cigars and pipe smoking as well.
Even if the person doesn't inhale, the toxins present in cigar and pipe smoke increase the chance of getting lung, mouth or throat cancer.

Secondhand Smoke

Environmental tobacco smoke is the smoke produced from both mainstream and sidestream smoke. When breathed in, it increases the risk of getting lung cancer.

Other causes of lung cancer include:

  • Radon is an invisible, odorless and tasteless radioactive gas that can be present in soil and rocks. People who work in mines are often exposed to radon gas, which may also be found in the foundations of homes in some parts of the United States. Radon causes damage to the lungs which can lead to lung cancer.
  • Asbestos is the name of a group of minerals that have the naturally occurring characteristic of a fibrous composition. When these fibers break apart and become airborne, they can be inhaled. They then lodge in the lungs, damaging cells and increasing the risk of lung cancer.
  • Pollution is suspected to increase the chance of getting lung cancer, especially breathing in the by-products from the combustion of diesel and fossil fuels. The links are not clear, but research is underway in this area.
  • Lung Disease such as tuberculosis (TB) appears to increase the risk of lung cancer. The cancer tends to form in the areas of the lung which have scar tissue from TB.
  • Personal history of lung cancer. If a person has had lung cancer once, it is more likely to recur. However, that risk is diminished if a person quits smoking.
Cancer and Lung Disease Resources:


National Cancer Institute / National Institutes of Health. What You Need to Know About Lung Cancer. Accessed January 2015.

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