Epithelioid Hemangioendothelioma

Published on 18/07/2015 by admin

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Last modified 18/07/2015

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 Enhancing (hyperemic) peripheral inner rim (increased vascularity)

image Nonenhancing peripheral outer rim or “halo” (avascular rim)
image Delayed or nonenhancing central part of tumor (myxoid and hyalinized stroma)
• Imaging protocol: Multiphasic CT or MR
• Spectrum of growth in lesions may be seen: Nodular form (more common); diffuse or extensive form (very rare)

image 
image 

TOP DIFFERENTIAL DIAGNOSES

• Peripheral cholangiocarcinoma
• Treated malignancy
• Focal confluent fibrosis
• Hemangioma (especially in cirrhotic liver)

PATHOLOGY

• Slowly progressing, low-grade, malignant vascular tumor of liver

image Most patients survive 5-10 years after diagnosis
• Must not be confused with infantile hemangioendothelioma

image Benign primary vascular liver tumor
image Resolves spontaneously in many cases

DIAGNOSTIC CHECKLIST

• Usually located at periphery with extension to capsule
• Typical capsular retraction of peripheral tumor (due to fibrosis and ischemia)

image Rule out other hepatic lesions that typically cause capsular retraction
• “Target” appearance on CECT or MR
• Differentiated from other lesions by tumor cells staining positive for factor VIII-related antigen
image
(Left) Axial CECT shows multiple peripheral, hypovascular lesions image with a “target” appearance (central lucency), typical CT findings of epithelioid hemangioendothelioma (EHE). The subcapsular lesions are associated with retraction of the overlying liver capsule image.

image
(Right) CT of the same patient shows more of the multicentric “target” lesions image typical of EHE, mostly in a peripheral location within the liver.
image
(Left) Gross pathology of the same liver after explantation shows the “target” appearance of the lesions, with necrosis and white fibrous tissue in the center of the lesions, as well as a peripheral rim of compressed parenchyma image and hyperemic tumor.

image
(Right) Central portion of EHE typically is hypocellular with loosely arranged spindle cells in a fibromyxoid or sclerotic stroma. The findings can simulate a scar or sclerosed hemangioma. (Courtesy S. Kakar, MD.)

TERMINOLOGY

Abbreviations

• Epithelioid hemangioendothelioma (EHE)

Synonyms

• Hepatic epithelioid hemangioendothelioma

Definitions

• Primary malignant tumor of liver arising from vascular elements of mesenchymal tissue

IMAGING

General Features

• Best diagnostic clue

image Coalescent peripheral hepatic nodules with target-like appearance and capsular retraction
• Location

image Liver

– Periphery (> 75%) with extension to capsule
image Locations other than liver

– Soft tissues, bone, and lung
• Size

image Varies from small tumor nodules to large confluent masses
• Key concepts

image Rare primary malignant (low-grade) vascular tumor of liver in adults
image Other primary malignant vascular tumors of liver

– Angiosarcoma (2% of all primary malignant liver tumors)
– Kaposi sarcoma: Metastatic vascular tumor in AIDS and transplant recipients
image All hepatic malignant vascular tumors

– Share histologic characteristics
– Grow around and into vessels
– Tend to be multifocal
image Clinical course

– Less aggressive than angiosarcomas or hepatocellular carcinoma, but still fatal in most cases
– Variable and unpredictable
– Metastatic in 40% of cases (spleen, mesentery, lymph nodes, lung, bone)

CT Findings

• Spectrum of growth in lesions may be seen

image Nodular form (more common)

– Multiple liver nodules coalesce to form large, confluent masses
image Diffuse or extensive form (very rare)
• Usually located at periphery with extension to capsule
• Capsular retraction (due to tumor fibrosis and ischemia) or flattening; segmental volume loss
• Occasional calcification within tumor
• Compensatory hypertrophy

image Uninvolved liver (usually left lobe)
• May have extrahepatic metastases and ascites
• NECT

image Tumor nodules

– Foci of homogeneous decreased attenuation (due to myxoid stroma) compared to normal liver parenchyma
image Conspicuity and extent of lesions

– CECT superior to NECT
• CECT

image Target-like enhancement pattern of tumor

– Delayed or nonenhancing central part of tumor (myxoid and hyalinized stroma)
– Enhancing (hyperemic) peripheral inner rim (increased vascularity)
– Nonenhancing peripheral outer rim or “halo” (avascular rim)

MR Findings

• T1WI

image Lesions are hypointense centrally
image Peripheral, thin, hypointense rim
• T2WI

image Hyperintense centrally
image Peripheral, thin, hypointense rim
• T1WI C+

image “Target” pattern: 3 concentric layers of alternating signal intensity (analogous to CECT appearance)

– Center: Hypointense
– Periphery: Thick, enhancing, inner rim and thin, nonenhancing, outer rim

Ultrasonographic Findings

• Grayscale ultrasound

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