Sex: female
Age: 45 years
History
Patient had no relevant previous history. Incidental finding on an ultrasound performed for ill-defined abdominal pain.
Laboratory data
No abnormalities.
Physical findings
None.
Case text
Ill-defined abdominal pain. Incidental finding of a hepatic lesion on ultrasound.
Image 1-4
Arterial and portal venous phase CT images of the liver .
Images 1,2: Arterial phase - 30s delay. Images 3,4: Portal venous phase - 40s delay.
Image 5-7
Axial breathhold T1 FLASH images of the liver (Images 5,6).
Coronal breathold T2 FSE images of the liver (Image 3).
Images 5,6: Axial breathold T1-weighted FLASH sequence: TR/TE; 160/6.6ms, flip angle 75°, 5mm slice thickness, matrix 129 x 256.
Image 7: Coronal breathold T2-weighted FSE sequence: TR/TE; 3300/138ms, flip angle 180°; slice thickness 5mm; matrix 116 x 256.
Image 8-13
Coronal and axial breathhold T1-weighted FLASH images of the liver, 20 minutes and 24 hours following infusion of contrast.
Coronal and axial breathold T1 FLASH sequence: TR/TE; 160/6.6ms, flip angle 75°,5mm slice thickness, matrix 129 x 256.
Image 13: Axial breathhold T1-weighted FLASH image 24 hours following infusion of contrast.
Image 1-4
1. What abnormalities are seen on Images 1 and 2?
Lobulated, well-defined, hypervascular mass in the right lobe of the liver, with prominent peripheral vessels, and a central non-enhancing scar.
2. What happens to these masses in the portal venous phase of enhancement on Images 3 and 4?
There is rapid washout of contrast from both masses of the liver during the portal venous phase.
3. What is your diagnosis? What is the differential diagnosis?
The larger mass has the characteristic CT appearances of focal nodular hyperplasia (FNH). The smaller mass in the left lobe of the liver could represent multifocal FNH. It may be an incidental haemangioma.
4. Is a central scar specific for FNH?
No. Central scars can be seen in several primary liver lesions, including a fibrolamellar carcinoma and cavernous haemangioma. Central scars are very rarely seen in hepatic adenomas.
Image 5-7
5 What abnormalities are seen on Images 5,6?
Lobulated, well-defined, mass in right lobe of the liver with prominent peripheral vessels. The signal intensity is similar to the liver, and homogeneous with a central low signal scar.
6. What abnormalities are seen on Image 7?
The lesion is difficult to see on T2-weigthed imaging as it has a similar low signal intensity to normal liver tissue. However high signal slow flow in the surrounding vessels are seen to be displaced around the mass. Note is also made of some high signal in the central scar which is characteristic of FNH.
Image 8-13
7. How many lesions can be seen on the early phase post Teslascan images (Images 8,10,12)?
Three lesions are seen on the 24 hour images. The largest lesion is now more hyperintense than the normal liver. Note that there is no uptake in the central scar.
In addition, a small lesion is seen anteriorly within the left lobe of the liver which is hyperintense and contains a low signal central scar (see Image 13).
There is also a hyperintense lesion more inferiorly in the left lobe of the liver, just to the left of the porta, which retains Teslascan uniformly on the delayed images (Image 11).
8. Why do these lesions take up and appear to retain Teslascan?
Focal nodular hyperplasia contains mainly normal hepatocytes, which explains why Teslascan is taken up in the first instance to a degree, which is similar to the normal liver on the early phase scans. However, these lesions do not have a normal biliary drainage, and therefore the contrast agent is not dealt with as efficiently as in normal liver. These lesions therefore are more conspicuous on the 24 hour scans. This aids in detecting the multifocal nature of the FNH in this particular case
Final diagnosis
Multifocal Focal Nodular Hyperplasia (Biopsy of the largest lesion = proof of diagnosis).
Differential diagnosis
1. Fibrolamellar hepatocellular carcinoma
2. Hepatic adenoma
Fibrolamellar hepatocellular carcinoma commonly has a central scar, which in contrast to FNH is low signal on T2-weighted images. Internal haemorrhage and necrosis are more commonly seen in fibrolamellar hepatocellular carcinoma and in hepatic adenoma.
Discussion
Focal nodular hyperplasia is a benign tumour-like condition that is thought to be a hyperplastic response to increased blood flow in an arterial malformation rather than a true neoplasm. It occurs in both sexes but is found most commonly in women (80-90%) in their third or fourth decade. FNH is solitary in 80% of cases but can be multifocal. Macroscopically FNH is lobulated and well defined with a pathognomonic central stellate scar with radiating fibrous septae dividing the lesion into lobules.
On CT, FNH is usually hypodense or isodense on precontrast scans, with rapid, marked enhancement in the arterial phase of scanning. During the portal venous phase FNH usually becomes isodense relative to normal hepatic parenchyma. The central scar is usually hypodense in the arterial phase but may show some contrast enhancement in the delayed phase.
MR imaging is probably the best modality in the diagnosis of FNH with a sensitivity of 70% and specificity of 98%. On MR imaging, FNH is typically isointense or slightly hypointense on T1-weighted imaging, and isointense or slightly hyerintense on T2-weighted images. The central scar is typically hypointense on T1- and hyperintense on T2-weighted images (2). In a recent MR paper with pathologic correlation, a central scar was seen in 30 of 37 cases (3). As FNH contains functioning hepatocytes it takes up hepatocyte specific contrast after the administration of contrast. The conspicuity of the lesions may be reduced on the early post contrast scans as the lesions may take up contrast to a similar degree to normal liver. However as the biliary system is disorganised in FNH, the contrast is not cleared as efficiently by the tumour as by normal liver on delayed scans and therefore its conspicuity is increased.