Lung cancer is the leading cause of cancer deaths in the United States and the world. There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Most forms of lung cancer are NSCLC.

Lung cancer is the abnormal growth of malignant cells in the tissues of the lungs or airways. NSCLC itself can be divided into subtypes, based on the kind of cells affected. The most common type of non-small cell lung cancer is adenocarcinoma. Other subtypes include squamous cell carcinoma and large-cell carcinoma.

Smoking tobacco is by far the largest risk factor for all types of lung cancer. About 87 percent of lung cancers are due to tobacco products, either through direct smoking or passive exposure to smoking, according to the American Cancer Society.

If caught early, surgery is often recommended to remove the malignant tumor. If the surgery is not successful, or the cancer has spread, radiation therapy may be recommended as a primary treatment. Chemotherapy also may be used as adjuvant therapy to surgery or to treat inoperable disease.

Lung cancers of all types often are not found until the cancer has advanced. The symptoms of lung cancer may not appear until the cancer has metastasized (spread) to other parts of the body. Common symptoms of lung cancer include persistent cough, breathing problems, blood in sputum, recurring respiratory infections, weight loss and fatigue.

Diagnosing NSCLC involves physical examination, blood tests, imaging tools (e.g., ultrasound, MRI, CAT scan), endoscopy and biopsy. Certain types of CAT scans offer some ability to screen for lung cancer, but studies on their effectiveness are still ongoing. The value of cancer screening may not be known for a number of years.

Whether to screen for lung cancer remains a decision to be made between the patient and the physician. The best method to prevent lung cancer of all types is by refraining from or quitting smoking.