What Is Lung Cancer?

Lung cancer is the uncontrolled growth of abnormal cells in one or both lungs. These abnormal cells do not carry out the functions of normal lung cells and do not develop into healthy lung tissue. As they grow, the abnormal cells can form tumors and interfere with the functioning of the lung, which provides oxygen to the body via the blood.

The Genetic Basis of Lung Cancer

All cells in the body contain the genetic material called deoxyribonucleic acid (DNA). Every time a mature cell divides into two new cells, its DNA is exactly duplicated. The cells are copies of the original cell, identical in every way. In this way our bodies continually replenish themselves. Old cells die off and the next generation replaces them.

A cancer begins with an error, or mutation, in a cell’s DNA. DNA mutations can be caused by the normal aging process or through environmental factors, such as cigarette smoke, breathing in asbestos fibers, and to exposure to radon gas.

Researchers have found that it takes a series of mutations to create a lung cancer cell. Before becoming fully cancerous, cells can be precancerous, in that they have some mutations but still function normally as lung cells. When a cell with a genetic mutation divides, it passes along its abnormal genes to the two new cells, which then divide into four cells with errors in their DNA and so on. With each new mutation, the lung tissue cell becomes more mutated and may not be as effective in carrying out its function as a lung cell. At a later stage of disease, some cells may travel away from the original tumor and start growing in other parts of the body. This process is call metastasis and the new distant sites are referred to as metastases.

Primary Versus Secondary Lung Cancer

Primary lung cancer starts in the lungs. The cancer cells are abnormal lung cells. Sometimes, people will have cancer travel from another part of their body or metastasize to their lungs. This is called secondary lung cancer because the lungs are a secondary site compared to the original primary location of the cancer. So, for example, breast cancer cells which have traveled to the lung are not lung cancer but rather metastatic breast cancer, and will require treatment prescribed for breast cancer rather than lung cancer.