Clinical Definition

Lung cancer is an uncontrolled, abnormal growth of cells that invades and destroys healthy pulmonary tissue. Symptoms can be due to the effects of the tumor in the lungs, metastases to distant sites or the activity of the cancer cells themselves. Smoking causes the vast majority of lung cancers. Treatments include chemotherapy, surgery, radiotherapy and other options.

In Our Own Words

The most common form of cancer worldwide, lung cancer is an uncontrolled growth of abnormal cells that destroys healthy tissue and can spread to other sites. Symptoms such as coughing and coughing up blood can occur due to the effects of the tumor locally, within the lungs. If some of the cancerous cells break away from the tumor, they can get to the bloodstream and trigger new tumor growths elsewhere, causing the cancer to spread. Such metastases are typically found in organs such as the liver, brain, bones and adrenal glands. It is estimated that about 90 percent of cancer cases are linked to smoking.

The two main types of lung cancer are non-small cell cancer and small cell cancer, named after how the cancerous cells appear under a microscope. Small cell cancers grow more quickly and are more likely to spread. Non-small cell lung cancers are further divided by type. Treatments include chemotherapy, surgery, radiation therapy and other methods.