It's not clear what causes most cases of liver cancer. But in some cases, the cause is known. For instance, chronic infection with certain hepatitis viruses can cause liver cancer.

Liver cancer occurs when liver cells develop changes (mutations) in their DNA — the material that provides instructions for every chemical process in your body. DNA mutations cause changes in these instructions. One result is that cells may begin to grow out of control and eventually form a tumor — a mass of cancerous cells.

July 24, 2013