Lung Cancer: Introduction
Lung cancer occurs when a malignant (cancerous) tumor grows inside the lungs, in structures such as the bronchi (small tubes that connect the windpipe to the inner surfaces of the lungs where gas transfer takes place). Like many other types of cancer, lung cancer is capable of spreading (metastasizing) to other parts of the body. In this case, cancer beginning in the lungs most commonly spreads to the brain, bones, adrenal glands and liver, via any of three mechanisms: direct extension, via the blood vessels, or via the lymph system. Direct extension occurs when a tumor grows rapidly in size such that it begins to touch an adjacent organ or structure, and then begins to penetrate itself into that adjacent organ or structure. Tumor cells are also able to get into the blood and lymph circulatory systems and travel, one by one, to distant structures.
Although lung cancer is difficult to treat and cure, it is for the most part preventable. Lifestyle choices can be made which can almost eliminate your risk for getting the disease. Your decision to stop smoking and to eat a healthy diet featuring plenty of fresh fruits and vegetables can greatly decrease your risk.
Types of Lung Cancer
Lung cancers are broken down into two major types, small cell lung cancer and nonsmall cell lung cancer. The difference between the two types involves where they originate, how fast they grow, and how they are best treated.
Small cell lung cancers are much less common than non-small cell cancers. This type of lung cancer originates in an inner layer of the walls of the bronchi called the bronchial submucosa, and grows aggressively (in comparison with non-small cell lung cancers), quickly spreading into surrounding tissues, and ultimately, through the body. Though the growth of this cancer is rapid, there are few or no clues that anything is particularly amiss. Symptoms are generally not noticeable until the cancer has spread into other parts of the body. Because of their rapid growth pace and tendency to metastasize, small cell cancers are described with only two stages (limited - when spread is contained to the localized area of the lung and immediate surrounding tissues, and extensive - when the cancer has spread throughout the body). By the time patients present for treatment, small cell lung cancers have generally reached their extensive stage. Treatment generally takes the form of a combined chemotherapy and radiation therapy approach.
Non-small cell lung cancers make up the vast majority of all lung cancers and can be broken down into three subtypes; squamous cell carcinoma, adenocarcinoma, and large cell lung cancer. Treatment of these types of cancer typically includes a combination of surgery, chemotherapy and radiation therapy.
Squamous cell carcinoma most often begins in the larger sections of the bronchi. It progresses slowest of all of the lung cancers.
Adenocarcinomas have the fastest growing incidence of any type of lung cancer in the United States, reported with frequency in both smokers and persons who never smoked. They typically occur at the periphery of the lungs, and grow more aggressively than squamous cell forms of lung cancer.
As the name suggests, large-cell lung cancers form as clusters of large undifferentiated cells. Like adenocarcinomas, they tend to occur at the periphery of the lung, growing and spreading more aggressively than squamous cell forms of lung cancer.