Type of liver cancer

Definition

Liver cancer is a form of cancer with a high mortality rate. Liver cancers can be classified into two types. They are either primary, when the cancer starts in the liver itself; or metastatic, when the cancer has spread to the liver from some other part of the body.

Description

Primary liver cancer

Primary liver cancer is a relatively rare disease in the United States, representing about 2% of all malignancies. It is, however, much more common in other parts of the world, representing from 10-50% of malignancies in Africa and parts of Asia. The American Cancer Society estimates that in 1998, at least 14,000 new cases of liver cancer will be diagnosed. It will also cause roughly 13,000 deaths in the United States in 1998.

In adults, most primary liver cancers belong to one of two types: hepatomas, or hepatocellular carcinomas, which start in the liver tissue itself; and cholangiomas, or cholangiocarcinomas, which are cancers that develop in the bile ducts inside the liver. About 90% of primary liver cancers are hepatomas. In the United States, about five persons in every 200,000 will develop a hepatoma; in Africa and Asia, over 40 persons in 200,000 will develop this form of cancer. Two rare types of primary liver cancer are mixed-cell tumors and Kupffer cell sarcomas.

There is one type of primary liver cancer that usually occurs in children younger than four years of age and between the ages of 12-15. This type of childhood liver cancer is called a hepatoblastoma. Unlike liver cancers in adults, hepatoblastomas have a good chance of being treated successfully. Approximately 70% of children with hepatoblastomas experience complete cures. If the tumor is detected early, the survival rate is over 90%.

Metastatic liver cancer

The second major category of liver cancer, metastatic liver cancer, is about 20 times as common in the United States as primary liver cancer. Because blood from all parts of the body must pass through the liver for filtration, cancer cells from other organs and tissues easily reach the liver, where they can lodge and grow into secondary tumors. Primary cancers in the colon, stomach, pancreas, rectum, esophagus, breast, lung, or skin are the most likely to spread (metastasize) to the liver. It is not unusual for the metastatic cancer in the liver to be the first noticeable sign of a cancer that started in another organ. After cirrhosis, metastatic liver cancer is the most common cause of fatal liver disease.

Causes & symptoms

Risk factors for primary liver cancer

The exact cause of primary liver cancer is still unknown. In adults, however, certain factors are known to place some individuals at higher risk of developing liver cancer. These factors include:

• Male sex. The male/female ratio for hepatoma is 4:1.
• Age over 60 years
• Exposure to substances in the environment that tend to cause cancer (carcinogens). These include a substance produced by a mold that grows on rice and peanuts (aflatoxin); thorium dioxide, which was used at one time as a contrast dye for x rays of the liver; and vinyl chloride, used in manufacturing plastics.
• Use of oral estrogens for birth control
• Hereditary hemochromatosis. Hemochromatosis is a disorder characterized by abnormally high levels of iron storage in the body. It often develops into cirrhosis.
• Cirrhosis. Hepatomas appear to be a frequent complication of cirrhosis of the liver. Between 30-70% of hepatoma patients also have cirrhosis. It is estimated that a patient with cirrhosis has 40 times the chance of developing a hepatoma than a person with a healthy liver.
• Exposure to hepatitis B (HBV) or hepatitis C (HBC) viruses. In Africa and most of Asia, exposure to hepatitis B is an important factor; in Japan and some Western countries, exposure to hepatitis C is connected with a higher risk of developing liver cancer. In the United States, nearly 25% of patients with liver cancer show evidence of HBV infection. Hepatitis is commonly found among intravenous drug abusers.

Symptoms of liver cancer

The early symptoms of primary, as well as metastatic, liver cancer are often vague and not unique to liver disorders. The long lagtime between the beginning of the tumor's growth and signs of illness is the major reason why the disease has such a high mortality rate. At the time of diagnosis, patients are often tired, with fever, abdominal pain, and loss of appetite. They may look emaciated and generally ill. As the tumor grows bigger, it stretches the membrane surrounding the liver (the capsule), causing pain in the upper abdomen on the right side. The pain may extend into the back and shoulder. Some patients develop a collection of fluid, known as ascites, in the abdominal cavity. Others may show signs of bleeding into the digestive tract. In addition, the tumor may block the ducts of the liver or the gall bladder, leading to jaundice. In patients with jaundice, the whites of the eyes and the skin may turn yellow, and the urine becomes dark-colored.

Diagnosis

Physical examination

If the doctor suspects a diagnosis of liver cancer, he or she will check the patient's history for risk factors and pay close attention to the condition of the patient's abdomen during the physical examination. Masses or lumps in the liver and ascites can often be felt while the patient is lying flat on the examination table. The liver is usually swollen and hard in patients with liver cancer; it may be sore when the doctor presses on it. In some cases, the patient's spleen is also enlarged. The doctor may be able to hear an abnormal sound (bruit) or rubbing noise (friction rub) if he or she uses a stethoscope to listen to the blood vessels that lie near the liver. The noises are caused by the pressure of the tumor on the blood vessels.

Laboratory tests

Blood tests may be used to test liver function or to evaluate risk factors in the patient's history. Between 50-75% of primary liver cancer patients have abnormally high blood serum levels of a particular protein (alpha-fetoprotein or AFP). The AFP test, however, cannot be used by itself to confirm a diagnosis of liver cancer, because cirrhosis or chronic hepatitis can also produce high alpha-fetoprotein levels. Tests for alkaline phosphatase, bilirubin, lactic dehydrogenase, and other chemicals indicate that the liver is not functioning normally. About 75% of patients with liver cancer show evidence of hepatitis infection. Again, however, abnormal liver function test results are not specific for liver cancer.

Imaging studies

Imaging studies are useful in locating specific areas of abnormal tissue in the liver. Liver tumors as small as an inch across can now be detected by ultrasound or computed tomography scan (CT scan). Imaging studies, however, cannot tell the difference between a hepatoma and other abnormal masses or lumps of tissue (nodules) in the liver. A sample of liver tissue for biopsy is needed to make the definitive diagnosis of a primary liver cancer. CT or ultrasound can be used to guide the doctor in selecting the best location for obtaining the biopsy sample.