Liver cancer is most often caused by long-term liver damage, particularly from chronic viral hepatitis infections, heavy alcohol use, and fatty liver disease. In 2022, there were over 866,000 new cases worldwide and nearly 759,000 deaths, making it one of the deadliest cancers. The majority of cases don’t appear out of nowhere. They develop after years or decades of inflammation and scarring that gradually push liver cells toward uncontrolled growth.
Cirrhosis: The Common Thread
Nearly all the major causes of liver cancer share one thing in common: they can lead to cirrhosis, which is severe, permanent scarring of the liver. Cirrhosis is the single biggest predictor of liver cancer regardless of what caused the scarring in the first place. Once cirrhosis develops, the annual risk of liver cancer ranges from about 2% to 4%, and that risk is highest in the first year after diagnosis, reaching roughly 8% before settling to around 3% per year going forward.
The connection is straightforward. When liver cells are damaged repeatedly, the body replaces them with scar tissue. The remaining healthy cells divide more frequently to compensate, and each round of division creates opportunities for DNA errors. Over time, those errors accumulate, and some cells begin growing without normal controls. This is why anything that causes chronic liver inflammation is considered a risk factor for liver cancer, even if the specific trigger varies widely from person to person.
Chronic Hepatitis B and C
Chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV) is the leading cause of liver cancer globally, driving most cases in East Asia, Southeast Asia, and sub-Saharan Africa. China alone accounted for nearly 368,000 new liver cancer cases in 2022, largely because of historically high hepatitis B rates.
For people with chronic hepatitis B who haven’t developed cirrhosis, the annual risk of liver cancer is less than 1%. But once cirrhosis sets in, that risk jumps to 2% to 3% per year. Hepatitis B is unusual among liver cancer causes because it can trigger cancer even without cirrhosis. The virus inserts its own DNA into liver cell genes, sometimes directly disrupting the tumor suppressor mechanisms that normally prevent cells from becoming cancerous.
Hepatitis C works somewhat differently. It rarely integrates into your DNA the way hepatitis B does, but it drives persistent inflammation that leads to fibrosis and eventually cirrhosis. The cancer risk from hepatitis C is concentrated almost entirely in people who have progressed to cirrhosis. Effective antiviral treatments now cure hepatitis C in most cases, which significantly reduces (but doesn’t completely eliminate) the long-term cancer risk, especially if significant scarring has already occurred.
Alcohol and Liver Damage
Heavy, sustained alcohol use is a major cause of liver cancer, primarily because it causes cirrhosis. Most alcohol-related liver cancers develop in people who already have cirrhosis from years of drinking. Regular consumption of 40 to 60 grams of alcohol per day, roughly three to four standard drinks, is associated with a meaningfully higher risk. For women, the threshold is likely lower.
Alcohol damages the liver through several routes. The body breaks alcohol down into a compound called acetaldehyde, which is directly toxic to liver cells and can damage DNA. Chronic exposure also triggers inflammation and promotes the buildup of scar tissue. People who drink heavily and also carry hepatitis B or C face a compounded risk that’s significantly greater than either factor alone. In meta-analyses, moderate to heavy drinkers (one or more drinks per day for women, two or more for men) had about a 42% higher incidence of liver cancer compared to light drinkers.
Fatty Liver Disease
Fatty liver disease tied to obesity, type 2 diabetes, and metabolic syndrome is the fastest-growing cause of liver cancer in Western countries. This condition, now called metabolic dysfunction-associated steatotic liver disease (MASLD), affects an estimated one in four adults worldwide.
For most people with fatty liver, the individual cancer risk is quite low: about 0.03 per 100 person-years when there’s no significant scarring. The risk climbs sharply, however, when the fat buildup triggers ongoing inflammation. People with active liver inflammation from fatty liver disease develop cancer at roughly 12 times the rate of those with fat deposits alone (5.29 versus 0.44 per 1,000 person-years). Once fatty liver progresses to cirrhosis, the annual incidence reaches 0.7% to 2.6%, comparable to cirrhosis from other causes.
What makes fatty liver disease particularly concerning is its sheer prevalence. Even though any one person’s risk may be small, the enormous number of people affected means fatty liver disease is producing a growing share of liver cancer cases, particularly in the United States, Europe, and parts of Latin America.
Aflatoxin Exposure
Aflatoxins are toxic compounds produced by molds that grow on improperly stored grains, corn, peanuts, and other crops in warm, humid climates. Aflatoxin B1, the most potent form, is a well-established cause of liver cancer, especially in parts of sub-Saharan Africa and Southeast Asia where contamination levels are high and hepatitis B is also common.
The mechanism is remarkably specific. Aflatoxin B1 causes a targeted mutation in a gene called TP53, one of the body’s most important tumor suppressors. This gene normally acts as a brake on cell growth, stopping damaged cells from multiplying. About half of liver cancers in high-aflatoxin regions carry this exact mutation, a signature fingerprint of aflatoxin exposure. When aflatoxin damage combines with chronic hepatitis B infection, the cancer risk multiplies dramatically because both are attacking different parts of the cell’s protective machinery at the same time.
Iron Overload and Hereditary Conditions
Hereditary hemochromatosis, a genetic condition that causes the body to absorb too much iron from food, is a potent but less common cause of liver cancer. Excess iron accumulates in the liver over decades, generating oxidative stress that damages cells and DNA. What’s striking about hemochromatosis is how strongly it’s linked to liver cancer even without cirrhosis: people with the condition but no cirrhosis have roughly 29 times the odds of developing liver cancer compared to matched individuals without the condition.
Other inherited conditions that increase risk include alpha-1 antitrypsin deficiency, which impairs the liver’s ability to produce a key protective protein, and Wilson’s disease, which causes copper to build up in the liver. These are rare, but they illustrate a broader principle: any condition that subjects the liver to chronic injury or toxic buildup can eventually lead to cancer.
How Normal Liver Cells Become Cancerous
Regardless of the initial trigger, liver cancer develops through a common biological process. Chronic damage forces liver cells to keep dividing to replace lost tissue. With each division cycle, there’s a small chance of acquiring a harmful genetic mutation. Over years, these mutations accumulate in key genes that control cell growth, self-destruction, and DNA repair.
Nearly half of liver cancer patients carry at least one recurring mutation in genes that regulate cell lifespan, growth signaling, or tumor suppression. One of the most common changes involves a gene that controls telomeres, the protective caps on chromosomes. When this gene is switched on inappropriately, cells gain the ability to divide indefinitely instead of aging and dying naturally. Other frequent mutations disable the TP53 tumor suppressor or activate growth-promoting signals that tell cells to multiply when they shouldn’t. No single mutation is enough on its own. It’s the gradual accumulation over a damaged liver’s lifetime of repair that tips cells from scarred but stable to cancerous.
Who Is Most at Risk
Liver cancer is two to three times more common in men than women, a gap that holds across nearly every country and every underlying cause. The reasons aren’t entirely clear, but higher rates of alcohol use, hepatitis infection, and differences in hormone signaling all likely contribute.
Geography matters enormously. Egypt has the highest age-adjusted incidence rate in the world at 32 per 100,000 people, driven largely by hepatitis C. Thailand and Vietnam follow at roughly 23 and 20 per 100,000, respectively, where hepatitis B is the dominant driver. In the United States, the rate is about 6.8 per 100,000, with fatty liver disease and hepatitis C as the primary contributors.
The strongest individual risk factors are having cirrhosis from any cause, carrying chronic hepatitis B or C, drinking heavily over many years, having diabetes alongside obesity, and living in regions with high aflatoxin contamination. Multiple risk factors acting together don’t just add up; they multiply. A person with both chronic hepatitis B and regular aflatoxin exposure, for instance, faces a far greater risk than either factor would produce alone. This layering effect is why liver cancer clusters so heavily in certain populations where several risk factors overlap.