DNA (deoxyribonucleic acid) is the genetic material that is found in all human cells. Your DNA is a code which contains instructions for producing all the characteristics of your body, such as your sex, your height, and your eye and hair colour. Half of your DNA is inherited from your father, and half is inherited from your mother.

Cancer

Cancer occurs when the structure of your DNA is suddenly changed. This is known as a genetic mutation. As well as providing your cells with instructions about your body's characteristics, DNA also provides them with instructions about when to grow, reproduce, and when to stop reproducing. However, the mutation in the DNA changes these instructions, so that the cells carry on growing. The cells continue to reproduce in an uncontrollable manner producing a lump of tissue known as a tumour. There are two types of tumour:

• benign - where the cancerous cells do not have the ability to spread beyond the tumour, and
• malignant - where the cells can spread beyond the tumour and affect other parts of the body.

The DNA in your cells can be changed by exposure to chemicals, or toxic substances. A toxic substance that causes cancer is known as a carcinogen. Many of the chemicals that are found in cigarettes are carcinogenic.

Your DNA can also be changed through exposure to radiation. However, in many cases of cancer, there is no clear reason why the DNA was changed.

Hepatocellular carcinoma (HCC) and cirrhosis

What causes the cells in the liver to become cancerous is still not entirely understood. However, cirrhosis (a serious condition that destroys healthy tissue) is known to be a major risk factor. Approximately 95% of people in the UK who develop HCC also have cirrhosis. In the past most cases of cirrhosis-associated HCC were due to alcohol abuse. However, in recent years, the leading cause of HCC is cirrhosis caused by the blood-borne viral infections, hepatitis B and hepatitis C.

A vaccination is available that can protect you against hepatitis B, but there is no vaccine for hepatitis C.

The number of cases of HCC has risen in the UK due to the associated rise of people infected with hepatitis C.

Alcohol abuse

The liver removes toxins, such as alcohol from your body. However, if you drink too much alcohol, your liver will be unable to cope with the amount of alcohol and will become damaged. It is hard to estimate the exact risk of people with alcohol-related cirrhosis developing HCC. This is because their natural life span is generally shortened by other factors related to alcohol abuse, though it may have been the case that many of these people would have developed HCC if they had lived longer.

Hepatitis B and Hepatitis C

Hepatitis B and Hepatitis C are both blood-born viral infections that can gradually cause damage to your liver over many years. In some people, the infections can be successfully treated but, in others, treatment is ineffective. People with hepatitis-related cirrhosis have approximately a 3-5% chance a year of developing HCC.

Autoimmune hepatitis

Autoimmune hepatitis is a rare inherited (genetic) condition where your immune system (the body's defence system that fights infection) attacks the cells of your liver as if they were a 'foreign' infection. What triggers this attack is unknown. The risk of developing HCC is very small because most cases of autoimmune hepatitis can be treated using medicines, known as immunosuppressants. stop the immune system from functioning.

Haemochromatosis

Haemochromatosis is another rare genetic condition where the body absorbs an excess amount of iron from food, leading to a build-up of iron in the body. The excess levels of iron have a toxic effect on the liver and cause cirrhosis. People with haemochromatosi-related cirrhosis have a 7-9% chance of developing HCC, although this risk falls to 1% once treatment begins to remove the iron from the body.

Non cirrhosis-related HCC

Fibrolamellar carcinoma

Fibrolamella carcinoma is a rare variation of HCC which accounts for less than 1% of cases of primary liver cancer. It normally appears in people who are between 20-40 years of age, and who have no associated history of cirrhosis. As fibrolamella carcinoma does not damage the whole of the liver, the outlook for those with the condition is much better than for those with HCC. However, the cancerous part of the liver will need to be removed, but as the liver is otherwise healthy, it should be able to function normally after the procedure.