Liver tumors may be noncancerous (benign) or cancerous (malignant). Cancerous liver tumors are classified as primary (originating in the liver) or metastatic (spreading from elsewhere in the body). Most liver cancers are metastatic. Cancers often spread to the liver because when cancer cells break away from cancer elsewhere in the body, they often enter and travel through the bloodstream, and the liver filters most of the blood from the rest of the body.
Noncancerous liver tumors are relatively common and usually cause no symptoms. However, rarely, these tumors cause the liver to enlarge or to bleed into the abdominal cavity.
Most noncancerous tumors are detected only when an imaging test—such as ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI)—is done for an unrelated reason. The liver usually functions normally even when a noncancerous tumor is present. Thus, results of blood tests to evaluate liver function are usually normal.
Fluid-filled sacs (cysts) sometimes form in the liver. Most cause no symptoms or health problems. They are detected incidentally by imaging tests. Rarely, people are born with many cysts in the liver (a disorder called polycystic liver disease). Usually, these people also have cysts in other organs, such as the kidneys (a disorder called polycystic kidney disease). The liver enlarges but usually continues to function well.
Last full review/revision January 2013 by Steven K. Herrine, MD