Liver cancer is the sixth most common cancer worldwide. Almost two thirds of cases occur in men and approximately 8 in 10 cases are in those aged 60 years or above.
Liver cancer is broadly categorised as primary and secondary.
Primary liver cancer
This cancer originates in the liver and its different forms of are named after the types of cells the cancer has developed from.
The two main types of primary cancer are:
Hepatoma i.e. hepatocellular carcinoma (HCC)
The most prevalent primary liver cancer. It affects the primary cells that constitute the liver, hepatocytes. Usually HCC is confined to the liver, but it may metastasize and spread to other organs.
The main risk factors for HCC are:
- Cirrhosis of the liver – Approximately three or four people out of a hundred with cirrhosis will go on to develop HCC each year. Cirrhosis is where the liver has become scarred as a result of damage over a long period of time. Therefore, any disease that causes cirrhosis can potentially lead to HCC, although certain causes of cirrhosis have a particularly strong link with HCC.
- Coinfection with viruses (e.g. hepatitis B, hepatitis C or HIV l) - chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV) is the worldwide leading cause for HCC. These infections lead to cirrhosis of the liver and are responsible for making liver cancer the most prevalent cancer in many parts of the world.
- Non-alcoholic steatohepatitis (NASH) - this is liver inflammation and damage due to the accumulation of fat in the liver. It is a member of a group of conditions called non-alcoholic fatty liver disease and is similar to the kind of liver disease that results from long-term alcohol abuse. While symptoms and problems are uncommon in many people, when they do occur, liver function is compromised which can possibly lead to cirrhosis.
- Obesity and type 2 diabetes – these are both associated with a higher risk of developing HCC, even more so if both are present.
- Heavy smoking – this has been linked with HCC particularly when present alongside excessive alcohol consumption or infection with viral hepatitis.
- Anabolic steroids – prolonged use may lead to liver tumours. These are usually benign but they can grow and rupture to cause pain.
- Inherited metabolic diseases - People with hereditary hemochromatosis absorb too much iron from ingested food. The iron settles in tissues throughout the body, including the liver. If enough iron accumulates in the liver, it can lead to cirrhosis and increase the risk of developing liver cancer.
- Rare diseases – Tyrosinemia, porphyria cutanea tarda, glycogen storage diseases, Wilson’s disease etc.
Biliary tree cancer (e.g. cholangiocarcinoma and gallbladder cancer)
Cholangiocarcinoma (bile duct cancer) is a rare but aggressive form of liver cancer that starts in the cells that line the bile duct. Unlike HCC, this form of primary cancer is more common in women than in men.
In most cases, there is no clear reason why cholangiocarcinoma develops but people suffering from the following problems are at a higher risk:
- Cirrhosis of the liver – as is the case with HCC, this scarring due to disease (e.g. HCV, HBV) and irritants (e.g. alcohol) can predispose a person to cholangiocarcinoma.
- Primary sclerosing cholangitis (PSC) – this is characterized by inflammation of the bile ducts (cholangitis) leading to scar tissue (sclerosis) formation. The cause of the inflammation is not usually known but the risk of this is increased by smoking.
- Bile duct stones – these can cause chronic inflammation that increases the risk of bile duct cancer.
- Rare diseases - Caroli syndrome, polycystic liver disease etc.
This is a rare variation of HCC usually found in people between 20 to 40 years old without cirrhosis being present. Fortunately, it is usually well contained and can be removed with surgery.
Secondary liver cancer
Also called metastatic cancer, this form occurs due to a cancer that first develops elsewhere in the body that then spreads (metastasizes) to the liver. The liver may be susceptible to this because it filters the blood - cancer cells in the bloodstream have a high chance of accumulating in the liver to establish a malignant tumour.
Those who are most at risk of secondary liver cancer are those with cancers of the large colon, pancreas, stomach, lung or breast.