Epithelioid haemangiomas of bone are benign intraosseous vascular neoplasms of epithelioid morphology which show locally aggressive behaviour.

Terminology

The following terms are not recommended ¹: 

• histiocytoid haemangioma
• haemorrhagic epithelioid haemangioma
• spindle cell haemangioma

Epidemiology

Epithelioid haemangiomas of bone are uncommon tumours with an unknown incidence. They have been observed in all age groups, with men being slightly more frequently affected ¹.

Diagnosis

The diagnosis of epithelioid haemangiomas of bone is made by typical pathological features and the location of the lesion ¹.

Diagnostic criteria

Diagnostic criteria according to the WHO classification of soft tissue and bone tumours (5^thedition) ¹:

• location primarily in bone
• epithelioid endothelial cell morphology with abundant eosinophilic cytoplasm

The following histological criterion is desirable:

• lobular structure with vessel formation

Clinical presentation

The most common complaint is pain. They are rarely found incidentally ¹.

Pathology

Epithelioid haemangiomas of bone are expansile vascular tumours with a lobular architecture sometimes showing cortical erosion and extension of the soft tissues ¹.

Location

About 18-25% of epithelioid haemangiomas of bone have been found in a multifocal regional distribution involving the following bones. The metaphysis or diaphysis is usually affected. There might be epiphysial involvement in paediatric patients.

• long tubular bones (≈40%)
• short tubular bones (feet > hands)
• flat bones
• vertebrae

Macroscopic appearance

Macroscopically epithelioid haemangiomas of bone are usually solid, soft, nodular, well-defined tumours of red colour due to haemorrhagic components which replace the bone marrow cavity ¹.

Microscopic appearance

Microscopic features of epithelioid haemangiomas include the following ¹:

• lobular architecture with large epithelioid, endothelial cells with eosinophilic cytoplasm
• arteriole-like vessels in the periphery of the lesions
• infrequent not atypical mitoses
• possibly small foci of necrosis
• stroma consisting of connective tissue sometimes with inflammatory infiltrates
• sometimes foci of intralesional haemorrhage

Immunophenotype

Immunohistochemistry stains are usually positive for endothelial markers such as CD31, CD34, FLI1, ERG or factor VIII-related antigen and might be positive for keratin or EMA.

Genetics

The pathogenesis of epithelioid haemangioma of bone involves a fusion including the FOS gene at 14q24.3 or the FOSB gene at 19q13.32 ¹.

Radiographic features

General imaging features of epithelioid haemangioma of bone are the following ^1-4:

• lobular architecture with vascular formations
• well-defined margins 
• intralesional septae
• expansile growth
• occasional cortical erosions and soft tissue extension

Plain radiograph

On plain radiographs epithelioid haemangioma will usually display the following characteristics ^1,3-5:

• expansile radiolucent, lytic or cystic-appearing lesions
• narrow transition zone
• endosteal scalloping

CT

Similar to plain radiographs CT will show expansile lytic or cystic lesions with an inner soft tissue component usually slightly lower than muscle density and no calcified or osteoid matrix ³.  

MRI

MRI will usually show lobulated lesions with surrounding bone marrow oedema and intralesional flow voids, otherwise, features of epitheloid haemangioma are non-specific ^1-4.

• T1: low to intermediate signal intensity
• T2: heterogeneous, intermediate to high signal intensity
• T1 C+ (Gd): avid homogeneous enhancement

Radiology report

The radiological report should include a description of the following:

• form, location and size
• tumour margins and transition zone
• cortical erosion, cortical breakthrough
• soft tissue component

Treatment and prognosis

Tumour management usually includes curettage or cryosurgery, rarely en bloc resection ^1,2. In inaccessible locations, the tumour has been irradiated ¹.

The prognosis is good with local recurrences in about 10%. Regional lymph node involvement has been observed, however, it is unclear whether this reflects metastatic deposits or multifocal disease ¹.

History and etymology

Epithelioid haemangiomas of bone were discovered in the 1960s ^6,7. Later soft tissue and bone lesions were summarised under the term ‘histiocytoid haemangioma’ by the pathologist Juan Rosai in 1979 ^6-8. This term was subsequently abandoned due to potential diagnostic confusion ^6,7.

Differential diagnosis

Conditions or tumours which can mimic the presentation and/or the appearance of epithelioid haemangiomas include ^1-5:

• angiosarcoma
• epitheloid haemangioendothelioma
• Langerhans cell histiocytosis
• enchondromatosis: in small tubular bones
• chondromyxoid fibroma
• giant cell tumour
• aneurysmal bone cyst

See also

• epithelioid haemangioma