What Is Lung Cancer?

Every moment that we are alive, cells in our bodies are dividing and reproducing – ten million of them every minute. Usually, there is an orderly pattern to this reproduction as cells develop and specialize to fit a particular need that the body has. Occasionally, though, a cell becomes damaged. There is a mutation in its DNA, and rather than maturing and dying as it is supposed to do, it continues to reproduce unchecked. In essence, this is cancer – uncontrolled reproduction and growth of abnormal cells in the body. Malignant cancer cells have the ability to invade nearby tissues and systems, or to migrate to other parts of the body (metastasizing).

Lung cancer is a growth of malignant cells in the lungs. Cancer of the lungs is one of the deadliest forms of cancer for several reasons. First, lung cancer tends to metastasize early in the progress of the disease. There’s much less time to fight the mutated cells with medication or radiation. In addition, when lung cancer does metastasize, it spreads to some very vulnerable and important organs. While it may spread to any organ in the body, lung cancer is most likely to metastasize to the adrenal glands, the liver, the brain and the bones.

Lung cancer can arise in any part of the lungs. Most cancer of the lungs (90-95%) are believed to start in the epithelial lining of the lungs – the linings of the large and small airways that perform the task of extracting oxygen from the air that we breathe. Because of this, lung cancer is sometimes called bronchogenic carcinoma – cancer arising from the bronchia. A smaller percentage of lung cancers begin in the pleura – the thin tissue sac that surrounds the lungs. Those cancers are called mesothelioma. The most common form of mesothelioma is linked to exposure to asbestos. Finally, the most rare type of lung cancers begin in the blood vessels or other supporting tissues in the lungs.

There are two main types of lung cancer – Small Cell Lung Cancer (SCLC) and Non-Small Cell Lung Cancer (NSCLC). SCLC is less common, but more deadly. It is inextricably linked to cigarette smoking – less than 1% of SCLC is diagnosed in non-smokers. SCLC is extremely aggressive and fast-moving. It metastasizes rapidly to other organs, and is most often not discovered until after it is already widespread.

NSCLC accounts for about 80% of all diagnosed lung cancers. There are three main types of non-small cell lung cancer – squamous cell cancer, adenocarcinomas and large cell carcinomas. It’s also possible for lung cancer to be mixed NSCLC types.

There are other far less common types of lung cancer. Bronchial carcinoids are small tumors that are most often found in people under 40 years of age. They grow more slowly, and are most amenable to treatment. Cancers can very rarely occur in the smooth muscle tissue or blood vessels that help support the lungs.

Finally, some cancers that are found in the lungs aren’t lung cancers at all. Because the lungs are so prone to metastatic cancers from other sites, it’s also not uncommon to find tumors from other primary cancers in the lungs. When those occur, they are most often scattered around the lungs in the peripheral tissues rather than in the central lung tissues.