What is a defining characteristic of focal nodular hyperplasia in the liver?

Focal nodular hyperplasia (FNH) in the liver is characterized by the presence of a central stellate scar. This scar is typically fibrous tissue that radiates from the center towards the periphery of the nodule, and it can often be a key feature seen on imaging studies such as MRI or CT scans. The presence of this scar is what distinguishes FNH from other hepatic lesions, such as hepatocellular adenomas or liver cancer.

The central stellate scar is significant not only for diagnosis, but also because it reflects the distinctive hyperplastic response of liver tissue, driven by abnormal vascularization and localized pathological changes, while maintaining a benign nature. FNH is generally asymptomatic and exhibits no increased risk of progression to malignancy, setting it apart from more dangerous hepatic neoplasms.

In contrast, the other options do not align with the typical features of FNH. For example, FNH is not associated with an increased risk of malignancy, which is a concern for some other liver lesions. Moreover, the imaging appearance of FNH is often heterogeneous rather than uniformly hypovascular, and necrosis is not a characteristic finding within these lesions.