Hemangioendothelioma
Synonyms and keywords: Infantile hemangioendothelioma; Kaposiform hemangioendothelioma; Retiform hemangioendothelioma; Epithelioid hemangioendothelioma; Dabska tumor

# Overview
Hemangioendothelioma is a rare group of mesenchymal vascular neoplasms. Hemangioendotheliomas commonly present with an enlarging mass and have been reported in the head, neck, lungs, lymph nodes, pleura, retroperitoneum, or stomach. Hemangioendotheliomas may be benign or malignant and tend to occur around medium to large venous structures. Hemangioendothelioma may be classified into 4 groups including epitheloid hemangioendothelioma (most common), kaposiform hemangioendothelioma, retiform hemangioendothelioma, and infantile hemangioendothelioma. The prevalence of hemangioendothelioma is approximately 1 per 100,000 individuals worldwide.
The majority of patients with hemangioendothelioma are symptomatic at the time of diagnosis. Early clinical features of hemangioendothelioma are often unspecific and may include abdominal pain, mass, weight loss, or fatigue. On CT scan, characteristic findings of hepatic hemangioendothelioma may include multiple hypo-attenuating lesions in both hepatic lobes which coalesce to form larger confluent hypo-attenuating regions in a peripheral or subcapsular distribution, halo or target pattern of enhancement in larger lesions, and a subcapsular lesion (with capsular retraction). Surgical resection, radiotherapy, and chemotherapy are often the treatment of choice for hemangioendothelioma.

# Historical Perspective
- Hemangioendothelioma was first described by Dr. Sharon Weiss, MD, an American pathologist, in 1986.

# Classification
- Hemangioendothelioma may be classified into 4 groups:
- Epithelioid hemangioendothelioma (most common)
- Kaposiform hemangioendothelioma
- Retiform hemangioendothelioma
- Infantile hemangioendothelioma
- Type I
- Multiple vascular channels
- Formed by an immature endothelial lining
- Stromal separation from bile ductules
- Type II:
- Disorganized appearance and hypercellular
- Bile ductules absent

# Pathophysiology
- The pathogenesis of hemangioendothelioma is characterized by epithelioid-like features.
- Hemangioendotheliomas tend to occur around medium to large venous structures.
- There are no genetic mutations associated with the development of hemangioendothelioma.
- On gross pathology, characteristic findings of hemangioendothelioma include:
- No hallmark features
- Size may range up to 18 cm
- On microscopic histopathological analysis, characteristic findings of hemangioendothelioma include:
- Large, epithelioid, perivascular cells
- Abundant, pale, eosinophilic cytoplasm
- Cytoplasmic vacuolation (some cells) (also known as "blister cells"), a key distinguishing feature
- May form lumen and contain red blood cells
- Vesicular nucleus with prominent nucleolus in some cells
- Tuft-like projections into capillaries
Papillary intralymphatic hemangioendothelioma
- Papillary tufts
- Central hyaline core lined by hobnail-like endothelial cells protruding into the lumina
Retiform hemangioendothelioma
- Infiltrative neoplasm composed of elongated, arborizing vessels
- Arranged in an anatomizing pattern
- Lined by a single layer of "hobnail-like" endothelial cells (protrude within the narrow lumina)
Kaposiform hemangioendothelioma
- Composed of several solid, poorly circumscribed nodules
- Nodules composed of a mixture of small capillaries and solid lobules
- Arranged in a glomeruloid pattern
- On immunohistochemistry, characteristic findings of hemangioendothelioma include:
- Positive CD31
- Positive CD34
- Positive Factor VIII

# Causes
- There are no established causes for hemangioendothelioma.

# Differentiating Hemangioendothelioma from Other Diseases
- Hemangioendothelioma must be differentiated from other diseases that cause a hypervascular mass, or abdominal pain, such as:
- Hepatoblastoma
- Hemangioma
- Angiosarcoma
- Colangiocarcinoma

# Epidemiology and Demographics
- Hemangioendothelioma is very rare. The prevalence of hemangioendothelioma is approximately 1 per 100,000 individuals worldwide.

## Age
- Patients of all age groups may develop hemangioendothelioma.

## Gender
- Hemangioendothelioma affects men and women equally.

## Race
- There is no racial predilection for hemangioendothelioma.

# Risk Factors
- Common risk factors in the development of hemangioendothelioma include:
- Oral contraceptives
- Polyvinyl chloride

# Natural History, Complications and Prognosis
- The majority of patients with hemangioendothelioma are symptomatic at the time of diagnosis.
- Early clinical features of hemangioendothelioma are often unspecific (e.g., abdominal pain, mass, weight loss, or fatigue).
- If left untreated, the majority of patients with hemangioendothelioma may progress to develop metastases.
- Common complications of hemangioendothelioma include:
- Hepatic failure
- Multi-organ failure
- Heart failure
- Prognosis is generally poor, and the 5-year survival rate of patients with hemangioendothelioma is approximately 55%.
Infantile hepatic hemangioendothelioma has a good prognosis.
- Infantile hepatic hemangioendothelioma has a good prognosis.

# Diagnosis

## Symptoms
- Hemangioendothelioma is usually asymptomatic.
- Symptoms of hemangioendothelioma may include:
- Abdominal pain
- Fatigue

## Physical Examination
- Patients with hemangioendothelioma usually may be well-appearing.
- Physical examination may be remarkable for:
- Palpation
- Large abdominal mass
- Hepatomegaly

## Laboratory Findings
- There are no specific laboratory findings associated with hemangioendothelioma.

## Imaging Findings
- On X-ray, characteristic findings of hemangioendothelioma include nonspecific soft tissue mass.
- When involving bone, hemangioendotheliomas are predominantly lytic and may mimic hemangiomas with a course honeycomb appearance
- On CT scan, characteristic findings of hemangioendothelioma include:
- Nonspecific soft tissue mass with density similar to muscle, but demonstrates bright contrast enhancement.
- Multiple hypo-attenuating lesions in both hepatic lobes
- Lesions coalesce to form larger confluent hypo-attenuating regions in a peripheral or subcapsular distribution
- Halo or target pattern of enhancement in larger lesions
- Subcapsular lesion often present with capsular retraction
- Located in a predominantly peripheral distribution, with coalescence as individual nodules
- Honeycomb appearance
- On MRI, characteristic findings of hemangioendothelioma include:
- T1: hypointense lesions relative to normal liver parenchyma on unenhanced T1-weighted images
- T2: heterogeneously increased signal intensity
- C+ (Gd): some lesions demonstrate either a peripheral halo or a target-type enhancement pattern after administration of a gadolinium-based contrast agent, with occasional observation of a thin peripheral hypointense rim
- On angiography, characteristic findings of hemangioendothelioma include dense, well-circumscribed areas of enhancement with early draining veins and shunting.

# Treatment

## Medical Therapy
- There is no treatment for hemangioendothelioma; the mainstay of therapy is supportive care.
- Common therapies for hemangioendothelioma may include:
- Interferon
- Sorafenib
- Corticosteroids
- Paclitaxel
- Thalidomide
- Doxorubicin
- Radiation therapy for hemangioendothelioma remains unclear.

## Surgery
- Surgery is the mainstay of therapy for hemangioendothelioma.
- The recurrence rate after surgery of hemangioendothelioma is approximately 40%.

## Prevention
- There are no primary preventive measures available for hemangioendothelioma.