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Hepatocellular carcinoma (HCC, also called hepatoma or hepatocarcinogenesis) is a primary malignancy (cancer) of the liver. Most cases of HCC are secondary to either a viral hepatitide infection (hepatitis B or C) or cirrhosis (alcoholism being the most common cause of hepatic cirrhosis). In countries where hepatitis is not endemic, most malignant cancers in the liver are not primary HCC but metastasis (spread) of cancer from elsewhere in the body, e.g. the colon. Treatment options of HCC and prognosis are dependent on many factors but especially on tumor size and staging.
Outside of the West, the usual outcome is poor, because only 10 - 20% of hepatocellular carcinomas can be removed completely using surgery. If the cancer cannot be completely removed, the disease is usually deadly within 3 to 6 months. This is partially due to late presentation with large tumours, but also the lack of medical expertise and facilities. This is a rare tumor in the United States.
HCC is one of the most common tumor worldwide. The epidemiology of HCC exhibits two main patterns, one in North America and Western Europe and another in non-Western countries, such as those in sub-Saharan Africa, central and Southeast Asia, and the Amazon basin. Males are affected more than females usually and it is more common between the 3rd and 5th decades of life Hepatocellular carcinoma causes 662,000 deaths worldwide per year.
In some parts of the world—such as sub-Saharan Africa and Southeast Asia—HCC is the most common cancer, generally affecting men more than women, and with an age of onset between late teens and 30s. This variability is in part due to the different patterns of hepatitis B transmission in different populations - infection at or around birth predispose to earlier cancers than if people are infected later. The time between hepatitis B infection and development into HCC can be years even decades, but from diagnosis of HCC to death the average survival period is only 5.9 months, according to one Chinese study during the 1970-80s, or 3 months (median survival time) in Sub-Saharan Africa according to Manson's textbook of tropical diseases. HCC is one of the deadliest cancers in China. Food infected with Aspergillus flavus (especially peanuts and corns stored during prolonged wet seasons) which produces aflatoxin, poses another risk factor for HCC.
North America and Western Europe
Most malignant tumors of the liver discovered in Western patients are metastases (spread) from tumors elsewhere. In the West, HCC is generally seen as rare cancer, normally of those with pre-existing liver disease. It is often detected by ultrasound screening, and so can be discovered by health-care facilities much earlier than in developing regions such as Sub-Saharan Africa.
Acute and chronic hepatic porphyrias (acute intermittent porphyria, porphyria cutanea tarda, hereditary coproporphyria, variegate porphyria) and tyrosinemia type I are risk factors for hepatocellular carcinoma. The diagnosis of an acute hepatic porphyria (AIP, HCP, VP) should be sought in patients with hepatocellular carcinoma without typical risk factors of hepatitis B or C, alcoholic liver cirrhosis or hemochromatosis. Both active and latent genetic carriers of acute hepatic porphyrias are at risk for this cancer, although latent genetic carriers have developed the cancer at a later age than those with classic symptoms. Patients with acute hepatic porphyrias should be monitored for hepatocellular carcinoma.
Hepatocellular carcinoma, like any other cancer, develops when there is a mutation to the cellular machinery that causes the cell to replicate at a higher rate and/or results in the cell avoiding apoptosis. In particular, chronic infections of Hepatitis B and/or C can aid the development of hepatocellular carcinoma by repeatedly causing the body's own immune system to attack the liver cells, some of which are infected by the virus, others merely bystanders. While this constant cycle of damage followed by repair can lead to mistakes during repair which in turn lead to carcinogenesis, this hypothesis is more applicable, at present, to Hepatitis C. In Hepatitis B, however, the integration of the viral genome into infected cells is the most consistently associated factor in malignancy. Alternatively, repeated consumption of large amounts of ethanol can have a similar effect. The toxin aflatoxin from certain Aspergillus species of fungus is a carcinogen and aids carcinogenesis of hepatocellular cancer by building up in the liver. The combined high prevalence of rates of aflatoxin and hepatitis B in countries like China and western Africa has led to relatively high rates of heptatocellular carcinoma in these regions. Other viral hepatitides such as hepatitis A have no potential to become a chronic infection and thus are not related to hepatocellular carcinoma.
Diagnosis, screening and monitoring
Hepatocellular carcinoma (HCC) most commonly appears in a patient with chronic viral hepatitis (hepatitis B or hepatitis C, 20%) or with cirrhosis (about 80%). These patients commonly undergo surveillance with ultrasound due to the cost-effectiveness.
In patients with a higher suspicion of HCC (such as rising alpha-fetoprotein and des-gamma carboxyprothrombin levels), the best method of diagnosis involves a CT scan of the abdomen using intravenous contrast agent and three-phase scanning (before contrast administration, immediately after contrast administration, and again after a delay) to increase the ability of the radiologist to detect small or subtle tumors. It is important to optimize the parameters of the CT examination, because the underlying liver disease that most HCC patients have can make the findings more difficult to appreciate.
On CT, HCC can have three distinct patterns of growth:
Once imaged, diagnosis is confirmed by percutaneous biopsy and histopathologic analysis.
The key characteristics on CT are hypervascularity in the arterial phase scans, washout or de-enhancement in the portal and delayed phase studies, a pseudocapsule and a mosaic pattern. Both calcifications and intralesional fat may be appreciated.
CT scans use contrast agents, which are typically iodine or barium based. Some patients are allergic to one or both of these contrast agents, most often iodine. Usually the allergic reaction is manageable and not life threatening.
An alternative to a CT imaging study would be the MRI. MRI's are more expensive and not as available because fewer facilities have MRI machines. More important MRI are just beginning to be used in tumor detection and fewer radiologists are skilled at finding tumors with MRI studies when it is used as a screening device. Mostly the radiologists are using MRIs to do a secondary study to look at an area where a tumor has already been detected. MRI's also use contrast agents. One of the best for showing details of liver tumors is very new: iron oxide nano-particles appears to give better results. The latter are absorbed by normal liver tissue, but not tumors or scar tissue.
Macroscopically, liver cancer appears as a nodular or infiltrative tumor. The nodular type may be solitary (large mass) or multiple (when developed as a complication of cirrhosis). Tumor nodules are round to oval, grey or green (if the tumor produces bile), well circumscribed but not encapsulated. The diffuse type is poorly circumscribed and infiltrates the portal veins, or the hepatic veins (rarely).
Microscopically, there are four architectural and cytological types (patterns) of hepatocellular carcinoma: fibrolamellar, pseudoglandular (adenoid), pleomorphic (giant cell) and clear cell. In well differentiated forms, tumor cells resemble hepatocytes, form trabeculae, cords and nests, and may contain bile pigment in cytoplasm. In poorly differentiated forms, malignant epithelial cells are discohesive, pleomorphic, anaplastic, giant. The tumor has a scant stroma and central necrosis because of the poor vascularization.
Staging and prognosis
Important features that guide treatment include: -
MRI is the best imaging method to detect the presence of a tumor capsule.
Abbreviations: HCC, hepatocellular carcinoma; TACE, transarterial embolization/chemoembolization; PFS, progression-free survival; PS, performance status; HBV, hepatitis B virus; PEI, percutaneous ethanol injection; RR, response rate; MS, median survival.
The Jade Ribbon Campaign is used for awareness of liver cancer in the Pacific Islands and will be introduced into America someday.
Jade is the official color of liver cancer.
Current research includes the search for the genes that are disregulated in HCC, protein markers, and other predictive biomarkers. As similar research is yielding results in various other malignant diseases, it is hoped that identifying the aberrant genes and the resultant proteins could lead to the identification of pharmacological interventions for HCC.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hepatocellular_carcinoma". A list of authors is available in Wikipedia.|