Cancer is a general term that describes the state in which cells divide uncontrollably. Cells are masses of protoplasm that make up all the tissues of the body and become specialized to develop into the body’s organs and structures, such as the bones, blood, nerves, muscles, and glands. Normally, cells grow, divide, and produce more cells to keep the body functioning properly.

Abnormal cells can accumulate and form growths or masses called tumors. Tumors can be benign (not cancer) or malignant (cancer) and can invade and destroy normal tissue. Cancer cells can spread through the bloodstream or lymphatic system to other parts of the body. The spread of a tumor from the original location to a new site is called metastasis.

Lung cancer is a disease that begins in the cells of the lungs. The lungs are a pair of sponge-like, cone shaped organs that are part of the respiratory system. The right lung has 3 sections, and the left lung has 2 sections. Each section is called a lobe. You may hear the term “bronchogenic cancer” used to refer to lung cancer. This is because most lung cancers begin in the cells of one of the breathing tubes (the bronchi) in the lungs.

There are several types of lung cancer. Learning about your particular type can help you talk with your doctor and other health care providers and make decisions about your treatment. The more informed you are, the more informed your questions and decisions will be.

Types of Lung Cancer

There are 2 main categories of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Of people diagnosed in the United States with lung cancer, 75% to 80% have non-small cell lung cancer, making it the most common type of lung cancer. Only 15% to 20% of people diagnosed with lung cancer have small cell lung cancer.

Non-Small Cell Lung Cancer (NSCLC)

There are 3 major subtypes of non-small cell lung cancer based on the appearance of their cells under the microscope:

•  Adenocarcinoma
•  Squamous cell carcinoma (formerly called epidermoid carcinoma)
•  Large cell undifferentiated carcinoma

Cure for NSCLC may be possible with surgery, if detected at an early stage. The following is a brief summary of the characteristics of each of the types of NSCLC:

Adenocarcinoma

•  Represents about 40% of the lung cancer cases in the United States
•  Is the most common lung cancer among women, in whom the number of cases is increasing
•  Usually starts near the outer edges of the lungs
•  May spread to other parts of the body
•  Can be seen in non-smokers
•  Includes subtypes such as bronchioalveolar adenocarcinoma (BAC)

Squamous Cell Carcinoma

•  Represents 30% to 35% of lung cancers in the United States
•  Occurs most frequently in men and older people of both sexes
•  Usually starts in one of the breathing tubes
•  Tends to remain localized in the chest longer than other types of lung cancer
•  Does not tend to metastasize early
•  Is strongly associated with smoking

Large Cell Undifferentiated Carcinoma

•  Represents about 5% to 15% of lung cancers in the United States
•  Incidence appears to be decreasing
•  May occur in any part of the lung
•  Tumors are usually large by the time they are diagnosed
•  Has greater possibility of spreading to the brain and mediastinum

Small Cell Lung Cancer (SCLC)

• Small cell lung cancer (also called “oat cell” because SCLC cells have the appearance of oat grains) is a more aggressive type of lung cancer than NSCLC. As stated earlier, SCLC is also less common than NSCLC.
•  Represents 15% to 20% of all lung cancers
•  Spreads to the lymph nodes and other organs more quickly than NSCLC
•  Is diagnosed predominantly in smokers or former smokers
•  Usually starts in one of the larger breathing tubes
•  Tends to grow rapidly
•  Commonly has spread by the time of diagnosis and is considered a systemic disease at the time of diagnosis
•  Is seemingly more responsive to a variety of chemotherapy drugs
•  Surgery is rarely utilized because of the early spread to other parts of the body

Mesothelioma

Although mesothelioma is not formally a type of lung cancer, it is a rare type of cancer of the mesothelium, the lining of the chest (the pleura), the heart, and the abdominal cavity. There are between 1,000 and 1,500 cases diagnosed each year in the United States. It occurs nearly 4 times more often in men than in women—especially white men over the age of 50.The major risk factor for developing this type of cancer is exposure to asbestos. Treatment depends on the stage of the disease, the health of the patient, and other factors. Surgery is the most common treatment. Radiation and chemotherapy may also be used. For specific information on the latest treatment, by stage, contact the National Cancer Institute at 1-800-4CANCER.