Metastases to the Liver

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What is Metastases to the Liver?

Liver metastases occur in the tissue of the liver, usually close to blood vessels. The liver has the second richest blood supply of the body, and therefore provides a very suitable environment for the growth of cancer cells.

The primary cancer site may be anywhere in the body, the most common sites are listed in "Predisposing Factors".

Who gets Metastases to the Liver?

The liver is the second most common site of metastasis (spread of cancer), after the lymph nodes. Liver metastases have been found in 30-70% of patients who are dying of cancer. In the Western world, metastasis to the liver is more common than primary liver cancer. Liver metastases are most commonly seen in patients aged 50-70.

Predisposing Factors

Most cancers can metastasise to the liver. The following are those most likely to cause liver metastases:

Eye

Lung

Brain tumours are virtually the only primary cancer that do not metastasise to the liver.

Cancer commonly spreads to the liver because it provides a suitable environment for the growth of tumour cells. Gaps in the lining of liver blood vessels allow tumour cells to get close to the functional cells of the liver (hepatocytes). The liver also has a rich blood supply, supplying tumour cells with the nutrients and oxygen they require to grow.

Progression

Liver metastases are foreign tissue growing within the liver. They either grow expansively (as a mass) or infiltratively (spreading through surrounding tissues). Physically, they grow and compress the surrounding liver tissue. A connective tissue rim is usually formed around the metastasis, and surrounding tissue is wasted away. Large metastases may even compress branches of the portal vein. Because they grow so quickly, liver metastases, like primary tumours, may outgrow their blood supply, resulting in death of the centre of the lesion.

Some specific cancer metastases have unique effects. Metastases from pancreatic and breast cancers result in fibrous scar formation. Some metastases throw off blood clots that may occlude the portal or hepatic veins. Others may cause areas of calcification that are readily detectable using radiographic imaging.

Metastases rarely cause death due to pure metastatic burden. Compression of the vena cava (hindering blood return to the heart), blockage of drainage outflows (resulting in lung infection, for example), and electrolyte imbalance caused by abnormal hormone secretion are some causes of death.

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