Hepatic epithelioid hemangioendothelioma (HEHE) is a rare, low- to intermediate-grade malignant hepatic vascular tumor.
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Epidemiology
There may be a greater female incidence (with reported M:F = 2:3), with peak incidence thought to be around the age of 30-40 years.
Pathology
Microscopic appearance
Histologically, the tumors are composed of dendritic and epithelioid cells. Tumor cells with intracytoplasmic lumina, occasionally containing red blood cells, appear as signet ring-like structures 2. They can be difficult to diagnose on the basis of biopsy results.
Radiographic features
They tend to be multiple solid tumor nodules located in a predominantly peripheral distribution, which coalescence into individual nodules. Lesions adjacent to the capsule often produce hepatic capsular retraction.
Ultrasound
Usually seen as hepatic lesions that are predominantly hypoechoic; however, hepatic lesions can also have mixed echotexture or be predominantly hyperechoic.
CT
Typically seen as multiple hypoattenuating lesions in both hepatic lobes that coalesce to form larger confluent hypoattenuating regions in a peripheral or subcapsular distribution, with a halo or target pattern of enhancement in larger lesions. Subcapsular lesions often present with capsular retraction. Hepatic or portal veins or their branches may taper and terminate at or just within the edge of these lesions (lollipop sign).
Calcification is uncommon but occurs on occasion.
MRI
T1: hypointense lesions relative to normal liver parenchyma on unenhanced T1-weighted images
T2: heterogeneously increased signal intensity, with a white target sign in which the bright central core is surrounded by a peripheral, slightly hyperintense halo
T1 C+ (Gd): some lesions demonstrate either a peripheral halo or a target-type enhancement pattern after administration of a gadolinium-based contrast agent, with an occasional thin peripheral hypointense rim
Ferumoxide-enhanced T2-weighted images may aid in distinguishing tumor margins.
Treatment and prognosis
The clinical course of these lesions can be variable with histological analysis being of little value in predicting the clinical outcome 1. The overall prognosis is much more favorable than for other hepatic malignancies 4.
Radical surgical resection and orthotopic liver transplantation are considered the treatments of choice 1,4. Due to the often multifocal nature of the tumor, transplantation may be the optimal treatment. Metastatic lesions have been reported in ~30% of patients at presentation and occur most commonly in the lungs 7. Other less common sites include the abdominal lymph nodes, omentum, mesentery, and peritoneum.
See also
epithelioid hemangioendothelioma (general article)