Lung cancer is one of the most common cancers in the world. It develops when malignant, or cancerous, cells form in the tissues of the lung.
People who smoke tend to be at greater risk for lung cancer, although nonsmokers may also be diagnosed with lung cancer, particularly if they are exposed to secondhand smoke or other environmental factors such as asbestos, arsenic or other substances in the workplace.
Other risk factors include radiation exposure, a family history of lung cancer and being infected with the human immunodeficiency virus (HIV).
Types of Lung Cancer
There are two main types of lung cancer, which are named for how large the cancer cells appear under a microscope: small cell lung cancer and non-small cell lung cancer.
Non-Small Cell Lung Cancer
Non-small cell lung cancer is the most common type of lung cancer. There are three main types of non-small cell lung cancer:
- Squamous cell carcinoma – Also called an epidermoid carcinoma, this type of cancer forms in the thin, flat cells lining the inside of the lungs.
- Large cell (undifferentiated) carcinoma – This type of cancer may begin in several types of large cells.
- Adenocarcinoma – This cancer begins in the cells the alveoli, which are tiny air sacs in the lungs.
Small Cell Lung Cancer
Small Cell Lung Cancer is less common and accounts for about 10% or 15% of lung cancer cases, according to the American Cancer Society.
Signs and Symptoms
Lung cancer does not always cause symptoms, and may be found during a chest X-ray done for another condition. However, if you experience any of the following, you should check with your doctor to see if they are caused by lung cancer or by other conditions:
- Chest discomfort or pain
- A cough that doesn’t go away or gets worse over time
- Difficulty breathing
- Wheezing
- Blood is mucus coughed up from the lungs
- Hoarseness
- Loss of appetite
- Weight loss for no known reason
- Fatigue, or feeling very tired
- Trouble swallowing
- Swelling in the face and/or veins in the neck
Lung Cancer Staging
The severity of the disease depends on the size and the extent of the tumor, and whether it has spread to other parts of the body. Physicians turn to a standardized staging system to better understand how far the cancer has spread and how to best treat it.
- Stage I – Cancer is found only in the lung.
- Stage II – Cancerous cells have spread to the nearby lymph nodes.
- Stage III – Cancer has spread to lymph nodes located in various areas of the chest.
- Stage IV – Cancer has spread to both lungs, into the area around the lungs or to distant organs.