What type of mass is characteristic of focal nodular hyperplasia on imaging?

Focal nodular hyperplasia (FNH) is characterized by a well-circumscribed mass on imaging studies. This is often seen as a homogeneous lesion with a characteristic central scar, especially on imaging modalities such as ultrasound, CT, or MRI. The mass typically demonstrates normal to mildly increased density without substantial necrosis or significant vascularity, distinguishing it from other liver lesions.

The lesion is often iso- to hypoechoic relative to liver tissue on ultrasound and has a typical appearance that helps differentiate it from malignant lesions. The well-circumscribed nature of FNH is an important feature because it implies a benign process, reinforcing that the mass has clear margins and is not infiltrating surrounding tissues. The central scar may enhance post-contrast, adding to the distinctive appearance of FNH.

While hypervascularity can be observed in some cases, it is not a definitive characteristic that stands alone compared to the clear, defined edges and the overall benign nature of the mass. Understanding these imaging characteristics is vital for proper diagnosis and management of liver lesions.