What is non-small cell lung cancer?

Non-small cell lung cancer (NSCLC) is a type of lung cancer in which cells in the lung grow abnormally and form a tumor. Lung cancers typically start in cells lining the bronchi and parts of the lung, such as the bronchioles or alveoli (Figure 1).

Approximately 85% of lung cancers are NSCLC.

There are three main types of NSCLC (Figure 2).

Adenocarcinoma – is the most common type of NSCLC. It affects women more than men. Adenocarcinoma is usually found in the outer parts of the lung (alveoli) and is often found before it has spread to other parts of the lung or body.
Squamous cell carcinoma – this type of NSCLC starts in squamous cells, (which are flat cells that line the inside of the lungs airways. It tends to be found in the middle part of the lungs, near one of the main airways (bronchi). Patients with squamous cell carcinoma often have a history of smoking. This type of cancer tends to grow and spread to other parts of the body quickly.
Large cell (undifferentiated) carcinoma – this type of NSCLC can be found in any part of the lung. It tends to grow and spread quickly, which can make it hard to treat.

All of the causes of lung cancer are not fully known. Some of the major risk factors are shown in Figure 3. Tobacco smoke is a known risk factor for lung cancer. Your risk for getting lung cancer is much higher if you have a history of smoking. Secondhand smoke is thought to cause more than 7,300 deaths from lung cancer each year among people who do not smoke. Of note, lung cancer can also occur in people who never smoked. Other risk factors for lung cancer include a family history of cancer or exposure to radon, asbestos, or air pollution. According to the US Environmental Protection Agency (EPA), radon is the second leading cause of lung cancer in the United States, and is the top cause of lung cancer in people who never smoked.