Ranging behind hemangiomas, focal nodular hyperplasias (FNH) are the second
most common benign solid liver lesions. Women between the age of 20 and 50
years are predominantly affected. In rare cases FNH may occur in children.
Etiologically, an arteriovenous Vascular malformation of the liver is disc
ussed, which causes pseudotumorous growth of the surrounding liver parenchy
ma. Morphological features such as the presence of a radial vascular archit
ecture and feeding arteries within a central scar are characteristic for th
e presence of FNH. Imaging techniques which enable the depiction of the art
erial blood supply with a characteristic centrifugal filling pattern, the c
ontrast enhancement in the early arterial phase, the absence of calcificati
ons and of a tumour capsule and the typical enhancement of the central scar
, are of particular importance. Knowledge of these features is important in
order to differentiate FNH from other hypervascular focal liver lesions wi
th tendency of scar formation, such as hepatic adenomas, giant hemangiomas,
hepatocellular and fibrolamellar carcinomas, and metastases. Diagnosis and
differential diagnosis of FNH will be enabled by a combined modality appro
ach consisting of (Doppler) sonography and triphasic CT. To confirm the dia
gnosis of FNH, dynamic MRI is advisable. Because of the invasiveness of ang
iography as well as the limited sensitivity and spatial resolution of the v
arious scintigraphic methods, these modalities no longer play a role in the
diagnostic workup of FNH. Lesions lacking typical features diagnostic for
FNH remain subjects for biopsy and histological examination.