The liver, located in the upper right part of the abdomen, is an organ responsible for filtering blood to remove harmful substances, regulating chemical levels in the blood, and producing bile to aid in digestion. A liver lesion is defined as an abnormal area, mass, or growth found within the liver tissue. These masses are often discovered incidentally during imaging procedures performed for unrelated health concerns.
Classification of Liver Lesions
Lesions are broadly categorized as either benign or malignant, which determines the level of clinical concern and subsequent management plan. Benign lesions are non-cancerous and do not typically spread to other parts of the body, while malignant lesions are cancerous and require intervention.
A secondary classification distinguishes between masses based on their internal composition. Lesions can be solid, meaning they are composed of tissue, or cystic, meaning they are fluid-filled sacs. The vast majority of liver lesions found are benign, and many are simple cysts discovered accidentally.
Common Benign Liver Lesions
The most frequently encountered non-cancerous mass in the liver is the hepatic hemangioma, which is an irregular tangle of blood vessels. These masses are extremely common, affecting a significant portion of the population. Hemangiomas are generally slow-growing and do not transform into cancer, meaning they rarely require any form of treatment. On specialized imaging, they exhibit a characteristic pattern of peripheral enhancement that gradually fills in toward the center.
Simple hepatic cysts are the second most common type of benign mass, presenting as thin-walled, fluid-filled sacs. These cysts are usually asymptomatic and have no potential for malignant transformation. Unless they grow large enough to cause pain or pressure on surrounding structures, they are typically left alone.
Another common benign mass is Focal Nodular Hyperplasia (FNH), which is a non-cancerous tumor believed to result from a localized hyperplastic response to an underlying vascular abnormality. FNH is composed of normal liver cell components—hepatocytes, bile ducts, and Kupffer cells—but arranged in an abnormal pattern. A defining feature of classic FNH visible on imaging is a central, non-enhancing scar. Because FNH rarely causes symptoms, its management typically involves confirmation of the diagnosis and no further action.
Malignant Liver Lesions
Malignant lesions, representing cancer in the liver, are divided into two main categories based on their origin. Primary liver cancer originates from the liver cells themselves, with Hepatocellular Carcinoma (HCC) being the most common type. HCC often develops in livers that are already damaged, most frequently in patients with cirrhosis resulting from chronic Hepatitis B or C infection, or long-term excessive alcohol consumption.
The second form of malignancy is metastatic liver cancer, which occurs when cancer cells from a primary tumor elsewhere in the body spread to the liver. Metastatic lesions are significantly more common in the United States than primary liver cancer. The liver is particularly susceptible to this process because all blood leaving the stomach and intestines passes through it before returning to the heart, carrying circulating cancer cells.
The most frequent sites of primary tumors that spread to the liver include:
- Colon
- Rectum
- Breast
- Lung
When cancer from the colon spreads to the liver, for example, the lesion is specifically classified as metastatic colorectal cancer, not liver cancer, because the cells in the liver mass are still colon cancer cells. The management of these secondary lesions is dependent on the type and stage of the original primary cancer.
Diagnosis and Management of Liver Lesions
The detection of a liver lesion almost always begins with diagnostic imaging, such as ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI). Ultrasound is often the initial screening tool due to its accessibility and low cost, but CT and MRI provide more detailed cross-sectional views. MRI, particularly when using specialized contrast agents, offers superior soft-tissue characterization, making it the preferred method for distinguishing between various lesion types.
The diagnostic process relies heavily on how the lesion appears and how it takes up and releases the injected contrast dye during the different phases of the scan. For many benign lesions, such as typical hemangiomas and FNH, the imaging characteristics are so distinct that a definitive, non-invasive diagnosis can be made.
A liver biopsy, which involves using a needle to remove a small sample of tissue for laboratory analysis, is generally reserved for indeterminate masses. Management of confirmed benign lesions often involves surveillance, meaning the lesion is monitored with periodic imaging to ensure it remains stable over time.