The liver, a large and complex organ, performs numerous functions essential for health. Like other organs, it can develop various conditions, including the formation of growths or lesions.
Understanding FNH
Focal Nodular Hyperplasia (FNH) is a benign, tumor-like lesion that forms in the liver. It is a non-cancerous growth and does not typically transform into malignant cancer. FNH is the second most common benign liver lesion, following hepatic hemangiomas. Its prevalence in the general population is estimated to be between 0.9% and 3.0%.
FNH is more frequently observed in women, particularly those between 20 and 50 years of age, with a female-to-male ratio often reported as 8:1. This lesion is composed of normal liver cells, including hepatocytes and Kupffer cells, but these cells are arranged in an abnormal, nodular pattern around a central fibrous scar. This central scar is a distinctive feature, though it may not be visible in all cases.
How FNH Develops and Presents
The formation of FNH is thought to stem from a localized vascular anomaly within the liver. This theory suggests that an abnormal blood supply, either increased (hyperperfusion) or decreased (hypoperfusion), triggers a reactive overgrowth of liver cells around the affected vessels. This process leads to the characteristic nodular architecture and the development of the central scar.
While FNH can enlarge in women using birth control, hormonal factors are not considered a primary cause of its development, a link largely unsupported by current research. Most individuals with FNH experience no symptoms, and the lesion is often discovered incidentally during imaging scans performed for other medical reasons. If symptoms do occur, they might include mild abdominal discomfort, a feeling of fullness, or, rarely, a palpable mass in the upper right abdomen.
Identifying and Managing FNH
FNH is primarily diagnosed through specialized imaging techniques, with Magnetic Resonance Imaging (MRI) being a preferred method due to its high sensitivity and specificity. Characteristic features on MRI, such as a central scar that enhances differently from the rest of the lesion, help distinguish FNH from other liver masses. Computed Tomography (CT) scans and ultrasound can also be used to further characterize the lesion.
A liver biopsy is rarely needed for a definitive FNH diagnosis, as imaging characteristics are often distinct enough. However, if imaging results are atypical or diagnostic uncertainty exists, a biopsy might be considered to rule out other conditions like hepatic adenoma or hepatocellular carcinoma.
Since FNH is benign and typically asymptomatic, most cases do not require active treatment, with watchful waiting being a common approach. This involves periodic imaging follow-ups to monitor the lesion’s size and stability. Intervention, such as surgical removal, is generally reserved for specific situations. These may include cases where there is persistent pain or discomfort clearly attributed to the FNH, diagnostic uncertainty despite advanced imaging, or very large lesions that cause significant symptoms due to mass effect. The prognosis for individuals with FNH is generally favorable.