What Is Lung Cancer?

There are 2 main types of lung cancer:

Non-small cell lung cancer

Most people with lung cancer have the type called non-small cell lung cancer (NSCLC). There are a few different types of non-small cell lung cancer. These include squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Though each of these sub-types starts in a different kind of cell in the lung, they're grouped together. They all have much the same treatment options and outlook (prognosis).

Small cell lung cancer

Small cell lung cancer (SCLC) is much less common than non-small cell lung cancer. SCLC is sometimes called oat cell cancer. (This is because the cells are shaped like oats when viewed under a microscope.) This type of lung cancer tends to grow and spread faster than non-small cell cancer.

Lung cancer can spread to the other lung, the liver, brain, or bones.

How cancer spreads

Cancer cells don’t always stay in one place. Cancer cells can break off from the place they first started. They can get into the bloodstream or lymph system and spread to other parts of the body. The lymph system is a network of nodes and vessels that help your body fight disease. It goes all over your body, much like your blood vessels do.

When cancer spreads, the process is called metastasis. Lung cancer that spreads (metastasizes) often goes to the other lung or the liver, brain, or bones. The cancer cells in these other parts of the body look like, act like, and are treated like the cancer in the lung. These are not new cancers. For instance, when lung cancer spreads to the brain, it's called metastatic lung cancer to the brain or lung cancer with brain metastasis. It's not brain cancer.