Case 17
History:
37 year old male with a hepatic lesion discovered on an outside CT scan for abdominal pain
Findings:
Multisequence abdominal MRI of the abdomen showing an isointense right hepatic lobe lesion indicative of hepatocellular origin with early intense enhancement and mild delayed de-enhancement.
Diagnosis:
Discussion:
Focal nodular hyperplasia (FNH) is the second most common benign liver tumor after hemangioma. FNH is classified into two types: classic (80% of cases) and nonclassic (20%). Magnetic resonance (MR) imaging has higher sensitivity and specificity for FNH than does ultrasonography or computed tomography (70%) and (98%) respectively.
About 1/3 of these lesions are isointense to liver parenchyma on both T1 and T2WI. Approximately 2/3 are slightly bright on T2 WI and slightly dark on T1WI. A central scar is present in approximately 65% of the cases and contains malformed vascular structures. Although not specific to FNH, the scar tend to be hypointense on T1 and hyperintense on T2 , that is in distinction to the scar seen with fobrolamellar carcinoma which tend to be hypointense on both T1 and T2 WI.
FNH demonstrates intense homogeneous enhancement during the arterial phase of gadolinium-enhanced imaging and enhancement of the central scar during later phases. The functional reticuloendothelial and hepatocellular features of FNH can be well demonstrated by scintigraphy. Approximately half of all cases of FNH demonstrate uptake of Tc-99m-labeled sulfur colloid.
