Lung Cancer: Patient Education

Cancer Facts

According to the American Cancer Society:

  • Lung cancer is by far the leading cause of cancer death among both men and women. Each year, more people die of lung cancer than of colon, breast, and prostate cancers combined.
  • Lung cancer mainly occurs in older people. About 2 out of 3 people diagnosed with lung cancer are 65 or older; fewer than 2 percent of all cases are found in people younger than 45. The average age at the time of diagnosis is about 71.


Lung cancer is the number one killer of both men and women in the United States today.

It begins when lung cells change into a mass or tumor, which can be either noncancerous (benign) or cancerous (malignant). In some cases, malignant tumors can grow uncontrollably and spread throughout your body through your lymph system or your bloodstream. When cancer has spread beyond its original location, it is said to have metastasized.

Primary lung cancer originates in the lung (the primary cancer site). If a cancer has begun in another organ and spread into your lungs, it is not considered lung cancer.

There are four main types of tumors that can develop in your lungs:

  • Non-small cell lung cancer (NSCLC)
    • Begins in the lining of your lungs
    • About 85 to 90 percent of lung cancers are NSCL
  • Small cell lung cancer (SCLC)
    • Begins in the nerve cells or hormone-producing cells in your lungs.
    • Called “small cell” because the cancer cells have a small appearance under a microscope
    • About 10 to 15 percent of lung cancers are SCLC.
  • Mesothelioma
    • Begins in the lining of the lungs, heart, chest cavity or abdomen
    • Usually caused by long-term exposure to asbestos
    • May also be benign
  • Carcinoid tumors of the lung
    • Are an uncommon type of neuroendocrine tumor that develops in your lung
    • Two kinds of carcinoid tumors of the lung:
      • Typical — slow growing and rarely spread
      • Atypical — faster growing and may spread to other organs

For more information, please select from the lung cancers listed above.

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Your Lungs

Your lungs are two large sponge-like organs inside your chest. Your right lung is divided into 3 lobes. Your left lung has 2 lobes (it’s smaller to leave room for your heart).

Your lungs are part of your respiratory system.

You breathe in through your nose or mouth and the air passes through your windpipe (trachea). Your windpipe splits into two tubes, called bronchi, which then divide into smaller branches, called bronchioles. Tiny air sacs at the end of the bronchioles are called alveoli.

As you breathe, the oxygen you take in through your lungs enters your bloodstream and runs through to your alveoli. In exchange, your blood picks up carbon dioxide, which leaves your body when you exhale. This exchange of oxygen and carbon dioxide is the main job of your lungs.

A thin lining called the pleura protects your lungs. The pleura helps your lungs expand and contract smoothly as you breathe.

The area between your lungs is called the mediastinum. The organs in this area include the:

  • Heart
  • Windpipe
  • Esophagus
  • Thymus
  • Lymph nodes

The thin muscle below your lungs separating your chest from your abdomen is your diaphragm.

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How Lung Cancer Begins and Spreads

In most cases, lung cancer begins in the cells that line your bronchi, bronchioles or alveoli.

Sometimes there are changes in the cells that are considered precancerous. They appear abnormal under a microscope, but they don’t necessarily form a mass and cannot be seen on most imaging tests.

In some cases, these precancerous cells may change and become cancerous. In doing so, they may cause new blood vessels to develop and nourish them. As they grow, they form a mass or a tumor that can be seen on imaging tests.

As the cancer grows, the cells may divide and spread (metastasize) to distant parts of your body.

Your lymph system is comprised of 3 parts:

  • Lymph nodes — small bean-shaped cells that fight infections
  • Lymphatic vessels — small tubes or veins that carry lymph
  • Lymph — clear fluid that contains immune system cells and that carries excess waste products from your tissues

Because the purpose of your lungs is to place oxygenated air in your bloodstream, lung cancer can often spread quickly through your bloodstream and lymph system, spreading cancer throughout your body, starting new tumors.

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Related Resources

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