Liver cancer happens when normal cells within the liver turn into abnormal cells and grow out of control. The liver is a huge organ within the upper right side of the belly. Most people who get cancer of the liver have long-term disease (also known as chronic liver disease). Having long-term liver disease will increase an individual's possibilities of getting liver cancer. the most common and most serious kind of long-term liver disease is a condition known as "cirrhosis," that scars the liver.