Focal nodular hyperplasia of the liver: radiologic-pathologic correlation.

Focal nodular hyperplasia (FNH) is a benign hepatic tumor that likely represents a local hyperplastic response of hepatocytes to a congenital vascular anomaly. It is most commonly seen in middle-aged women and is typically a solid mass measuring less than 5 cm in diameter. Most lesions have central scars that contain thick-walled vessels that provide excellent arterial blood supply; hemorrhage, necrosis, and infarction are, therefore, extremely unusual. Characteristic imaging features include a hypervascular homogeneous tumor with a central scar and with both hepatocellular and reticuloendothelial function. Ultrasonography, computed tomography, scintigraphy, and magnetic resonance imaging all offer different advantages in the detection and characterization of FNH. There is excellent correlation between the pathologic and imaging features of FNH. In many cases, it is possible to obtain a prospective imaging diagnosis of FNH; however, in some cases, the distinction between FNH and other primary hepatic neoplasms is not possible. In these latter cases, close imaging follow-up, needle biopsy, or even surgical resection may be necessary.