The liver is the largest organ in the body, located below the right lung. Divided into right and left lobes, it is made of hepatocytes, a type of cell that processes nutrients in the blood.
The main functions of the liver are to absorb nutrients from the blood and to make bile, a fluid that helps digest fats. The liver breaks down and stores many of the nutrients absorbed from the intestine and helps remove toxic wastes from the body. In addition, the liver produces certain proteins that help stop bleeding from a cut or injury.
Unlike most other organs, the liver gets blood from two sources: the hepatic artery, which supplies the liver with oxygen-rich blood, and the portal vein, which carries nutrient-rich blood from the intestines to the liver. The liver also has the rare capacity to rebuild itself within a few weeks, even after a substantial portion has been removed.
How Liver Metastases Arise
Most malignant (cancerous) liver tumors arise when cancer spreads (metastasizes) from another part of the body to the liver. Cancer cells that break away from the original (primary) tumor may be carried through the bloodstream to the liver, which filters the blood. These cancer cells occasionally stick to the liver, where they form new tumors called metastases. Depending on the origin of the tumor, a liver metastasis can spread rapidly or develop years after the original tumor was treated.
The portal vein, which carries blood from the intestines to the liver, also carries cancer cells that break away from tumors in patients with colon cancer. As a result, most liver metastases begin from colon cancer. Approximately 60 to 70 percent of people with colorectal cancer eventually develop a liver tumor. In fact, the liver is the only site of metastasis in up to 35 percent of patients with metastatic colorectal cancer.1 Liver metastases that develop from cancer in the breast, esophagus, stomach, pancreas, lungs, kidneys, and skin (melanoma) are much less common. Doctors treat metastatic liver tumors based on the original location of the cancer, although it is not always possible to identify its origin.
Liver metastases are more common in the United States and Europe than primary liver cancer (hepatocellular carcinoma), a rare type of cancer that begins in the liver.
Many patients with liver metastases have either no symptoms or non-specific symptoms that could be attributed to a variety of health conditions. If symptoms occur, they may include:
- general feeling of poor health or weakness
- loss of appetite
- weight loss
- swelling of the legs
- abdominal pain or discomfort
J.S. Tomlinson, W.R. Jarnigan, R.P. DeMatteo, Y. Fong, P. Kornprat, M. Gomen, N. Kemeny, M.F. Brennan, L.H. Blumgart, M. D'Angelica, Actual 10-year survival after resection of colorectal liver metastases defines cure. Journal of Clinical Oncology 2007 25(29): 4575-9.[PubMed Abstract]