females. Even with surgery prognosis is poor with most individuals not living longer than six months after diagnosis. Only 3% of individuals live longer than two years. Hepatoblastoma Another type of cancer formed by liver cells is hepatoblastoma, which is specifically formed by immature liver cells. It is a rare malignant tumor that primarily develops in children, and accounts for approximately 1% of all cancers in children and 79% of all primary liver cancers under the age of 15. Most hepatoblastomas form in the right lobe. Metastasis to liver Many cancers found in the liver are not true liver cancers but are cancers from other sites in the body that have spread to the liver (known as metastases). Frequently, the site of origin is the gastrointestinal tract, since the liver is close to many of these metabolically active, blood-rich organs near to blood vessels and lymph nodes (such as pancreatic cancer, stomach cancer, colon cancer and carcinoid tumors mainly of the appendix), but also from breast cancer, ovarian cancer, lung cancer, renal cancer, prostate cancer. Children The Children's Oncology Group (COG) has developed a protocol to help diagnose and manage childhood liver tumors. Causes Viral infection Viral infection with hepatitis C virus (HCV) or Hepatitis B virus (HBV) is the chief cause of liver cancer in the world today, accounting for 80% of HCC. Men with chronic HCV or HBV are more likely to develop HCC than women with chronic HCV or HBV; however, the reasons for this gender difference is unknown. HBV infection is also linked to cholangiocarcinoma. The role of viruses other than HCV or HBV in liver cancer is much less clear, even though there is some evidence that co-infection of HBV and hepatitis D virus may increase the risk for HCC. HBV and HCV can lead to HCC, because these viral infections cause massive inflammation, fibrosis, and eventual cirrhosis occurs within the liver. In addition, many genetic and epigenetic changes are formed in liver cells during HCV and HBV infection, which is a major factor in the production of the liver tumors. The viruses induce malignant changes in cells by altering gene methylation, affecting gene expression, and promoting or repressing cellular signal transduction pathways. By doing this, the viruses can prevent cells from undergoing a programmed form of cell death (apoptosis) and promote viral replication and persistence. HBV and HCV also induce malignant changes by causing