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Liver cancer, also known as hepatic cancer, is a cancer that originates in the liver. Liver tumors are discovered on medical imaging equipment (often by accident) or present themselves symptomatically as an abdominal mass, abdominal pain, yellow skin, nausea or liver dysfunction. The leading cause of liver cancer is cirrhosis due to either hepatitis B, hepatitis C, or alcohol. In 2013, 300,000 deaths from liver cancer were due to hepatitis B , 343,000 to hepatitis C and 92,000 to alcohol.〔 Liver cancers are not the same as liver metastases, which start in another part of the body and spread to the liver. Liver cancers are formed from either the liver itself or from structures within the liver, including blood vessels or the bile duct. Primary liver cancer is globally the sixth most frequent cancer, and the second leading cause of cancer death. In 2012 it occurred in 782,000 people and resulted in 746,000 deaths.〔 Higher rates of liver cancer occur where hepatitis B and C are common, including East-Asia and sub-Saharan Africa. Five year survival rates are 17% in the United States.〔(【引用サイトリンク】url=http://seer.cancer.gov/statfacts/html/livibd.html )〕 Hepatic is from the Greek ''hêpar'', meaning "liver".〔(【引用サイトリンク】title=''Hepato-'' Etymology )〕 ==Classification== The most frequent liver cancer, accounting for approximately 75% of all primary liver cancers, is hepatocellular carcinoma (HCC) (also named ''hepatoma'', which is a misnomer because adenomas are usually benign). HCC is a cancer formed by liver cells, known as hepatocytes, that become malignant. 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. Liver cancer can also form from other structures within the liver such as the bile duct, blood vessels and immune cells. Cancer of the bile duct (cholangiocarcinoma and cholangiocellular cystadenocarcinoma) account for approximately 6% of primary liver cancers.〔 There is also a variant type of HCC that consists of both HCC and cholangiocarcinoma. Tumors of the blood vessels (angiosarcoma and hemangioendothelioma, embryonal sarcoma and fibrosarcoma are produced from a type of connective tissue known as mesenchyme. Cancers produced from muscle in the liver are leiomyosarcoma and rhabdomyosarcoma. Other less common liver cancers include carcinosarcomas, teratomas, yolk sac tumours, carcinoid tumours and lymphomas.〔 Lymphomas usually have diffuse infiltration to liver, but It may also form a liver mass in rare occasions. Many cancers found within 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 (such as colon cancer and carcinoid tumors mainly of the appendix), but also from breast cancer, ovarian cancer, lung cancer, renal cancer, prostate cancer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Liver cancer」の詳細全文を読む スポンサード リンク
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