Imaging findings
Modalities: US,
CT (nonenhanced and enhanced),
MRI (T1,
T2,
Diffusion,
ADC,
T1C+ sequences) PET-FDG,
arteriography.
Ultrasound:
On ultrasound HEH presents as multiples peripheral hypoechoic masses or mixed hypo-hyperechoic masses,
with a hypoechoic rim.
(Fig. 5, Fig. 6)
In diffuse lesions,
US shows areas of overall decreased echogenicity that contain,
in some cases,
calcified foci.
There is no correlation between sonographic pattern and the size of the lesion.
CT:
Unenhanced CT images reveal nodular foci of decrease attenuation because of their myxoid stroma.
In diffuse lesions,
precontrast CT scans show large and confluent areas of overall low attenuation.
After contrast administration,
the tumor takes a small amount of contrast medium in the central zone and sometimes areas of hyper vascularization can be detected.
The tumor enhancement pattern is similar to a target or halo, produced by a nonenhanced outer rim of avascular tissue juxtaposed with an enhanced inner peripheral rim.
Depending on the predominance of myxoid and hyalinized elements and the degree of central fibrosis,
the center of the tumor may appear enhanced or non enhanced,
on delayed phase.
The vascularity of diffuse lesions is moderate but delayed enhancement is consistent with fibrosis.
(Fig. 7 , Fig. 8)
Central calcifications,
areas of necrosis or hemorrhage can be also seen on CT.
MRI
MRI reveals the target aspect of the lesion: hypointense centrally with a peripheral thin hypointense rim in T1-weighted images,
hyper intense centrally surrounded by lower signal intensity and peripheral thin hypointense rim in T2-weighted images.
After contrast administration,
the target pattern is more evident,
with three concentric layers: a thick enhancing inner rim,
a thin nonenhancing outer rim and a hypointense central zone.
A delayed central enhancement can usually be seen in larger lesions.
(Fig. 9,
Fig. 10)
Imaging of CT and MR are similar.
Changes in hepatic contours are more evident in diffuse lesions,
including capsular retraction which is centered over a peripheral mass and suggestive for HEH,
but not specific.
In addition,
a compensatory enlargement,
usually in the left and caudate lobe in patient with predominant lesions located in the right lobe,
may be seen.
Portal vein tumor thrombus,
obliteration of hepatic veins or sign of portal hypertension may be also encountered.
Two radiological signs are particularly interesting:
1. The capsular retraction adjacent to hepatic tumors is not common,
although this finding has been described in a variety of tumors: hepatic carcinoma,
cholangiocarcinoma,
colorectal metastases,
hemangioma or confluent fibrosis.
Many radiologists consider this sign to be associated with central cholangiocarcinoma but it was first described in epitheloid hemangioendotelioma.
(Fig. 11)
2. The ”lollipop sign” is a characteristic radiological aspect which show the abrupt "cut-off" of the hepatic or portal vein.
(Fig. 12, Fig. 13)
PET-FDG:
In some case reports on positron-emission tomography (PET) scan,
an increased fluorodeoxyglucose (FDG) uptake by HEH has been described.
PET demonstrates moderate to intense uptake in the tumors, also seen in adjacent lymph nodes and extrahepatic sites of disease,
and has a potential interest for staging desease or to detect recurrences.
(Fig. 14)
Arteriography: hyper vascular,
hypo vascular or avascular lesions,
based on the degree of sclerosis and hyalinization.
Major differential diagnosis
Hemangioma (especially in cirrhotic liver)
Hemangiomas are likely to decrease in size due to progressive cirrhosis.
Capsular retraction is a rare finding and was described in a very few cases in non-cirrhotic liver.
(Fig. 16)
Focal confluent fibrosis
Capsular retraction is associated with segmental or lobar shrinkage and it is common in advanced cirrhosis.
( Fig. 19)
Treated hepatocellular carcinoma or metastases
There is a history of chemotherapy or resection for liver tumor.
Capsular retraction is common whereas some treated metastases may show cystic or necrotic transformation.
Cholangiocarcinoma
Hepatic cholangiocarcinoma presents like a heterogeneous mass with capsular retraction,
sometimes with satellite lesions and intrahepatic duct dilatation.
(Fig. 18)