A mass on the liver is an area of abnormal tissue found during an imaging test like an ultrasound, CT scan, or MRI. In most cases, it’s not cancer. Roughly 15% of the general population has a benign liver lesion, and many of these are discovered accidentally when imaging is done for an unrelated reason. Still, the word “mass” can feel alarming, so understanding the different types and what they mean for your health is important.
Liver masses fall into three broad categories: benign (noncancerous) growths, primary liver cancers that start in the liver itself, and metastatic tumors that have spread to the liver from cancer somewhere else in the body. The next steps your doctor recommends depend entirely on which category the mass falls into.
Benign Liver Masses
The majority of liver masses turn out to be harmless. The two most common noncancerous, solid liver lesions are hemangiomas and focal nodular hyperplasia (FNH). Hepatic adenomas are less common but carry slightly more clinical significance.
Hemangiomas
A hemangioma is a tangle of blood vessels inside the liver. It’s the single most common benign liver tumor, usually found in middle-aged women, and it ranges in size from a few millimeters to over 5 centimeters. Most hemangiomas cause no symptoms at all and are discovered by chance. They can grow in response to estrogen and progesterone, which partly explains why they’re more frequent in women. Small hemangiomas almost never need treatment and are typically left alone after a confident diagnosis on imaging.
Focal Nodular Hyperplasia
Focal nodular hyperplasia is a solid mass thought to develop because of a disruption in blood flow within the liver. Like hemangiomas, it occurs more often in adult women and rarely causes symptoms. Larger ones sometimes show a distinctive central scar on imaging that helps doctors identify them without a biopsy. FNH does not become cancerous and generally requires no treatment.
Hepatic Adenomas
Hepatic adenomas are rarer and worth paying closer attention to. They have a strong link to oral contraceptive use: the annual incidence jumps from about 1 per million in non-users to 30 to 40 per million in women taking birth control pills. Risk climbs further after more than two years of use, and one study found a 25-fold increase in relative risk among women who had used oral contraceptives for more than nine years compared to those who used them for less than one year. Anabolic steroid use and certain metabolic conditions like glycogen storage disease also raise the risk.
Why adenomas matter more than other benign masses: they carry a small risk of becoming cancerous, and larger ones (over about 7 cm) located near the liver’s surface can rupture and bleed. Stopping oral contraceptives often causes the tumor to shrink on its own. In some cases, surgical removal is recommended.
Primary Liver Cancer
When a liver mass is malignant and originates in the liver itself, the most likely diagnosis is hepatocellular carcinoma, or HCC. It accounts for more than 90% of primary liver tumors. The connection to chronic liver disease is overwhelming: HCC develops in roughly 80% to 90% of patients who already have cirrhosis. Chronic hepatitis B, chronic hepatitis C, heavy alcohol use, and nonalcoholic fatty liver disease are the main underlying conditions that lead to cirrhosis and, eventually, cancer risk.
A less common primary liver cancer is cholangiocarcinoma, which starts in the bile ducts inside the liver. It behaves differently from HCC and is treated differently as well.
On imaging, malignant masses tend to look different from benign ones. They often have blurry, irregular edges rather than sharp borders. They may show a characteristic “washout” pattern on contrast-enhanced scans, where the mass lights up quickly with contrast dye and then fades faster than the surrounding liver tissue. Invasion into blood vessels within the liver is another hallmark of cancer, seen most often with HCC.
Metastatic Liver Tumors
The liver is one of the most common places in the body for cancer to spread. When a mass on the liver is metastatic, it means cancer started in another organ and traveled to the liver through the bloodstream. Colorectal cancer is the leading source of liver metastases by a wide margin. Pancreatic and breast cancers are the next most common origins. In women under 50, breast cancer is a particularly frequent source. In people over 70, the primary cancer is most often gastrointestinal.
Metastatic liver tumors often appear as multiple masses rather than a single one, which can help distinguish them from a primary liver cancer or a benign growth. If you’ve already been diagnosed with cancer elsewhere, a new mass on the liver will naturally raise concern about spread.
Symptoms of a Liver Mass
Most liver masses, whether benign or malignant, produce no symptoms when they’re small. The liver is a large organ with a lot of reserve capacity, so a growth can exist for a long time without causing problems you’d notice. This is why so many masses are found incidentally during imaging ordered for something else entirely.
When symptoms do develop, they typically reflect either the size of the mass pressing on surrounding structures or the loss of normal liver function. Common signs include upper abdominal pain (especially on the right side), unintentional weight loss, loss of appetite, nausea, fatigue, and abdominal swelling. Jaundice, a yellowing of the skin and whites of the eyes, signals that bile flow is being blocked or the liver is struggling. White or chalky-colored stools, visible veins on the abdomen, and unusual bruising or bleeding are less common but more concerning signs.
How Liver Masses Are Diagnosed
Imaging is the first and most important tool. Ultrasound often catches the mass initially, and a follow-up CT scan or MRI with contrast dye usually provides enough detail to narrow down the type. Radiologists look at the mass’s borders, how it absorbs and releases contrast dye over time, and whether it invades nearby blood vessels. Many benign masses, particularly hemangiomas and FNH, have imaging patterns distinctive enough that no further testing is needed.
Blood tests play a supporting role. A protein called alpha-fetoprotein (AFP) is sometimes elevated in liver cancer. At the standard cutoff used in clinical practice, AFP correctly identifies about 70% of liver cancers and correctly rules it out about 90% of the time. However, its sensitivity drops to roughly 49% for early-stage cancers, meaning it misses about half of small tumors. AFP is most useful for monitoring people already known to be at high risk, like those with cirrhosis, rather than as a standalone screening tool.
A biopsy, where a needle is guided into the mass to collect a tissue sample, is reserved for situations where imaging and blood work don’t give a clear answer. If the mass has features that could be either benign or malignant, or if there’s more than one possible diagnosis, a biopsy provides definitive information. Image guidance with ultrasound, CT, or MRI is used during the procedure to place the needle precisely. Biopsies aren’t routine for every liver mass because many can be confidently diagnosed without one, and the procedure carries small risks of bleeding and discomfort.
What Happens After a Mass Is Found
Your next steps depend entirely on the type of mass. A small hemangioma or FNH diagnosed confidently on imaging may need nothing more than a single follow-up scan to confirm stability, and some don’t even require that. Hepatic adenomas are monitored more closely, and your doctor may recommend stopping hormonal medications to see if the mass shrinks.
If the mass is suspicious for cancer, the process moves faster. Additional imaging, blood work, and possibly a biopsy will be used to confirm the diagnosis and determine the extent of disease. For primary liver cancer, treatment options range from surgical removal to targeted therapies, depending on the size, number of tumors, and overall liver health. For metastatic disease, the treatment plan centers on the original cancer type.
The single most reassuring fact is that the vast majority of incidentally discovered liver masses are benign. A mass on an imaging report is a finding that needs clarification, not an automatic reason for alarm.