A liver mass, also known as a hepatic lesion, is an abnormal growth or area of tissue detected within the liver, typically found during an imaging scan performed for an unrelated reason. The discovery of such an abnormality can cause concern, but most growths are benign and pose little risk to health. Masses in the liver are a common finding, especially as individuals age. A professional medical evaluation is necessary to determine the specific nature of the mass, confirming if it is non-cancerous, malignant, or a non-tumorous condition like a fluid-filled sac or infection.
Common Benign Liver Growths
The most frequently encountered non-cancerous solid masses in the liver are vascular malformations called hemangiomas. These lesions consist of tangled masses of blood vessels and are the most common type of benign liver tumor, occurring in up to 5% of adults in the United States. Hemangiomas are typically small, do not cause symptoms, and rarely require treatment.
Another common benign finding is Focal Nodular Hyperplasia (FNH). This is a tumor-like growth made up of liver cells, bile duct elements, and connective tissue surrounding a central, star-shaped scar. FNH is often found in younger women and is considered benign, meaning it does not progress to cancer. Like hemangiomas, FNH masses are usually discovered incidentally and can often be left alone without the need for removal.
Hepatocellular adenomas are less common benign tumors that originate from the main liver cells (hepatocytes). They primarily affect women of childbearing age and have historically been associated with the use of oral contraceptives, suggesting a hormonal influence. Although not cancerous, adenomas require careful monitoring because they carry a small risk of spontaneous bleeding or, in rare cases, malignant transformation. Discontinuation of hormonal medications is often the first step in management to attempt to shrink the lesion.
Malignant Liver Masses
When a mass is determined to be malignant, or cancerous, it is essential to distinguish between those that originated in the liver and those that spread from another site in the body.
Primary liver cancer, known as Hepatocellular Carcinoma (HCC), arises directly from the liver’s main cells. The vast majority of HCC cases develop in the setting of long-standing liver disease, particularly cirrhosis. Cirrhosis is often caused by chronic Hepatitis B or C infection, excessive alcohol consumption, or non-alcoholic fatty liver disease.
HCC is the most prevalent form of primary liver cancer, but Cholangiocarcinoma is the second most common. Cholangiocarcinoma develops from the cells lining the bile ducts within or outside the liver. The risk factors for this type are distinct from HCC and include conditions like primary sclerosing cholangitis and parasitic infections in certain geographic regions.
Far more common than primary liver cancer is secondary, or metastatic, cancer. This occurs when cancer cells from a tumor elsewhere in the body travel to the liver. The liver’s extensive blood supply makes it a frequent site for metastasis from cancers originating in organs like the colon, lung, or breast. These metastatic masses are still classified and treated based on their tissue of origin. For example, a mass in the liver that started in the colon is treated as metastatic colorectal cancer, not primary liver cancer. The treatment approach and prognosis depend heavily on whether the cancer is primary or metastatic.
Non-Neoplastic Causes of Liver Masses
Not every mass detected in the liver is a true solid tumor (neoplasm); some are related to fluid accumulation or inflammation. Simple hepatic cysts are fluid-filled sacs that are common, affecting approximately 5% of the general population. These cysts are harmless, cannot become cancerous, and rarely cause symptoms unless they grow large enough to create pressure or discomfort.
Another distinct type of mass is an abscess, which is a localized collection of pus caused by a bacterial or parasitic infection. Pyogenic, or bacterial, liver abscesses are serious conditions that require urgent medical attention and treatment. Treatment often involves a combination of antibiotics and draining the collection of pus. While an abscess may appear as a mass on imaging, it is an inflammatory process rather than a growth of abnormal cells.
Severe inflammation or localized injury can also sometimes create masses that mimic tumors on imaging, often termed pseudotumors or inflammatory masses. These can include conditions like focal fatty change, where an area of the liver either accumulates or is spared from fat deposition. These non-neoplastic lesions are typically resolved by treating the underlying cause, such as an infection or inflammatory condition, and are not related to uncontrolled cell growth.
How Doctors Determine the Mass Type
The diagnostic journey begins after an initial mass is found, usually with further advanced imaging studies to better characterize the lesion. Specialized imaging techniques like multiphasic CT scans or MRIs with contrast agents are used. Doctors observe how the mass takes up and releases the injected dye, providing clues about its internal structure and blood flow. Certain enhancement patterns can be highly indicative of specific benign masses, such as a hemangioma or FNH, potentially avoiding the need for more invasive procedures.
Blood tests are also an important part of the work-up, primarily to assess liver function and to check for specific tumor markers. Liver Function Tests (LFTs) can indicate the degree of inflammation or damage to the organ. A protein called Alpha-Fetoprotein (AFP) may be measured, as its elevation can sometimes suggest the presence of Hepatocellular Carcinoma. These lab results help build the clinical picture alongside the imaging findings.
When imaging results are inconclusive or there is a strong suspicion of malignancy, a biopsy is typically performed to obtain a definitive diagnosis. This procedure involves inserting a fine needle, often guided by ultrasound or CT, to retrieve a small tissue sample from the mass. A pathologist then examines the cells under a microscope to determine the exact cell type, which is the most reliable way to distinguish between a benign growth, a non-neoplastic condition, or a specific type of cancer.