Lung cancer is a disease in which cancer cells grow in the lungs.

Lung Cancer

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Lung cancer occurs when cells in the lung divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and can spread to other parts of the body. A benign tumor does not invade or spread.

Lung cancers that start in the lungs are divided into two types:

    
  • Non-small cell lung cancer—This type generally grows and spreads more slowly. Non-small cell lung cancer accounts for the majority of the lung cancer cases that are diagnosed each year in the United States. The most common types of non-small cell lung cancer are squamous cell cancer and adenocarcinoma.
  • Small cell lung cancer—This type generally grows more quickly. It is more likely to spread to other parts of the body.
  • Most cases of lung cancer are associated with tobacco use, such as:

        
  • First- or second-hand cigarette smoke
  • Pipe or cigar smoking, chewing tobacco
  • While most cases of lung cancer are due to smoking, a percentage of people with lung cancer have never smoked, nor have they been exposed to secondhand smoke.