All tissue is made of cells and in healthy individuals, cells reproduce according to the same design as the old ones. When old cells die, new ones take their place. Cancer cells occur when old cells fail to die or when new cells form when they are not needed. This collection of cells mass together and form a tumor. Tumors may be benign (non cancerous) or malignant (cancerous).

Benign tumors often do not require removal nor do they threaten a person’s life. Malignant tumors, however, do need to be removed as they are a threat to life. They may also return after removal and can spread throughout the body, affecting other organs and systems. When cancer cells spread throughout the body, it is referred to as metastasis. When someone is diagnosed with lung cancer and it spreads (metastasis) the next step is to determine how wide spread the cancer is or what stage the cancer is at.

Staging is an important aspect of lung cancer treatment as it determines how far advanced the cancer has spread. Lung cancer tends to spread to the lymph nodes, brain, adrenal glands, the liver, and throughout the bones. As cancer cells spread throughout the body, they attach themselves to other areas or organs. They do not change their original type, however. Lung cancer cells continue to be lung cancer whether they have spread through the blood, bones, or liver. When the cancer spreads it is referred to as metastatic lung cancer, regardless of where the cancer cells are located. Therefore, lung cancer that has spread to the liver would be treated as lung cancer and not liver cancer.