Asked by Scott, Prince Edward Island, Canada
Are cysts on the liver necessarily cancerous?
Conditions Expert
Dr. Otis Brawley
Chief Medical Officer,
American Cancer Society
Dear Scott: The quick answer to your question is no. There are many non-cancer-related causes of cystic masses in the liver. Indeed, simple liver cysts are almost always asymptomatic and found incidentally during routine testing for something else. These masses are not cancerous and not even dangerous.
Simple cysts of the liver contain fluid. This can be seen on liver imaging with ultrasound or CT scanning. They are found in about 1 percent of adults and are more common in women than men. They are usually a few millimeters in size. Very rarely, they can be large and need to be treated because of size and the discomfort they cause.
Physical examination, blood studies and ultrasound findings are usually sufficient to distinguish simple cysts from other less-common lesions that can appear cystic. Occasionally, a CT scan is needed to make the distinction, and rarely a needle biopsy or surgical resection is done to make the diagnosis.
Lesions that can look like simple cysts include a liver abscess; a cancerous tumor with a necrotic or dead liquid center; and a hemangioma, which is a benign collection of blood vessels, which can look like cancer. A cystadenoma is a benign cystic lesion that is rarely found. It is treated with surgical removal, as it can progress to a cancer called cystadenocarcinoma.
Polycystic liver disease is a condition of multiple benign liver cysts. It occurs in some patients with polycystic kidney disease.
Polycystic kidney disease is a disease of multiple simple cysts of the kidney. It tends to be inherited. These lesions are watched and not usually treated.
The most interesting liver cysts I have personally seen were a series of hydatid cysts caused by the Echinococcus. The Echinococcus is a parasite. Humans acquire it from exposure to the feces of infected dogs or sheep. These cysts have to be surgically removed in an operation in which the surgeon has to be careful not to spread the disease. Hydatid cysts of the liver are uncommonly encountered in the United States.
Note: The above discusses cystic lesions of the liver. There are a number of solid lesions that can be found in the liver. The liver is a common site for the spread of colon, breast and lung cancer. These lesions are usually solid and rarely cystic. Patients will have probably been diagnosed with their cancer before the lesions are seen in the liver. Nodular liver non-cancerous diseases with solid masses are also common. They can be due to alcoholic liver disease, rheumatologic diseases and other causes.
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