A liver nodule is a mass of cells within the liver tissue. These growths are typically discovered unintentionally during an imaging scan, such as an ultrasound or CT, performed for an unrelated medical issue. The term “nodule” is purely descriptive and does not define whether the mass is harmless or poses a serious threat. Careful evaluation is necessary to determine its exact nature and the appropriate next steps for the patient.
Benign Versus Malignant
The primary concern is whether the growth is benign (non-cancerous) or malignant (cancerous). Fortunately, the majority of incidentally detected liver nodules are benign and do not spread to other parts of the body. The most common benign lesion is a hemangioma, which is a tangle of abnormal blood vessels found in up to 7% of adults.
Another frequent non-cancerous growth is Focal Nodular Hyperplasia (FNH), a mass of liver cells often characterized by a central scar visible on imaging. Hepatocellular adenomas are less common but are more significant because they carry a small risk of transforming into cancer and a greater risk of rupture and internal bleeding. These benign lesions are usually managed with surveillance. Adenomas, particularly those larger than five centimeters or found in men, often require removal.
Malignant liver nodules fall into two main categories: primary liver cancer and metastatic cancer. The most common primary liver cancer is Hepatocellular Carcinoma (HCC), which develops from the main liver cells. HCC is strongly associated with underlying chronic liver disease, such as cirrhosis caused by Hepatitis B or C infection or chronic alcohol use.
Metastatic cancer involves nodules that originated from a primary tumor elsewhere in the body, such as the colon, lung, or breast, and traveled to the liver. For patients with chronic liver disease, any new nodule is suspicious for HCC and requires urgent characterization. Conversely, a nodule in a person with a history of cancer outside the liver is often presumed to be metastatic disease.
How Liver Nodules Are Discovered and Evaluated
The initial detection of a liver nodule is followed by specialized imaging to characterize the mass. Ultrasound is often the first tool used, but it lacks the detail needed for a definitive diagnosis. Physicians utilize multi-phase Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scans with intravenous contrast dye.
These dynamic scans track how the nodule takes up and releases the contrast dye over various time phases, providing distinct vascular patterns. For example, HCC often exhibits intense enhancement during the arterial phase, followed by a rapid “washout” during the later portal venous phase. Benign lesions, such as hemangiomas, show a characteristic pattern of peripheral enhancement that slowly fills in toward the center.
Blood tests, including liver function tests and tumor markers such as alpha-fetoprotein (AFP), may be performed. While elevated AFP levels can support an HCC diagnosis, the test is not definitive, and a normal result does not rule out cancer. If imaging results are inconclusive or the patient has a high-risk history, a liver biopsy may be necessary.
A biopsy involves using a fine needle to extract a tissue sample from the nodule for analysis by a pathologist. This provides the most accurate diagnosis for indeterminate masses. However, a biopsy is often avoided for lesions with classic benign imaging features, such as hemangiomas, due to the risk of bleeding.
Treatment and Long-Term Monitoring
The management strategy for a liver nodule depends on its confirmed nature, size, and the patient’s liver function. For small, asymptomatic nodules definitively identified as benign, such as hemangiomas or FNH, the approach is “watchful waiting” with no active treatment. Surveillance may be recommended only for very large hemangiomas or when the diagnosis remains uncertain.
Hepatocellular adenomas often require intervention, especially if they are large due to the risk of rupture and internal bleeding. For malignant nodules like HCC, treatment options are guided by the tumor size, number, location, and underlying liver function. Curative therapies include surgical resection, which removes the tumor and a margin of healthy tissue, or liver transplantation for advanced cases.
Non-surgical treatments are common for tumors that cannot be safely removed or transplanted. These include:
- Ablation techniques, such as radiofrequency ablation (RFA) or microwave ablation (MWA), which use heat to destroy small tumors.
- Embolization procedures, like chemoembolization, which deliver chemotherapy or radiation directly to the tumor while cutting off its blood supply.
- Systemic treatments, including targeted therapy and immunotherapy, reserved for advanced or widespread disease.