Retiform haemangioendothelioma

Retiform haemangioendotheliomas or hobnail haemangioendotheliomas are intermediate locally aggressive and rarely metastasising vascular neoplasms with a distinctive hobnail endothelial cell morphology.

Epidemiology

Retiform haemangioendotheliomas are rare with <100 cases reported in the literature ¹. They have been described in a wide age range, but most commonly in young adults and children ^1,2. There seems to be no gender predilection ¹.

Associations

In exceptional situations cases were associated with the following ^1-3:

• previous radiation therapy

• lymphoedema including Milroy disease

• cystic lymphangioma

Diagnosis

The diagnosis of retiform haemangioendothelioma is established histologically.

Diagnostic criteria

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

• ramified vascular channels with a tree-like appearance

• bland endothelial cells with a hobnail appearance

• no or very low mitotic activity

Clinical presentation

Retiform haemangioendotheliomas usually appear as slow-growing, red-coloured bluish skin lesions. They have been described as soft and compressible and are usually smaller than 3 cm upon diagnosis ^1,4.

Pathology

Retiform haemangioendotheliomas are characterised by a distinctive hobnail endothelial cell morphology and a typical branching, arborizing vascular pattern ¹.

Aetiology

At the time of writing the aetiology of retiform haemangioendotheliomas remains unknown ¹.

Location

Retiform haemangioendotheliomas usually affect the dermis and subcutaneous tissue of the distal extremities, especially the lower limb ¹.

Macroscopic appearance

Macroscopically retiform haemangioendotheliomas are sometimes characterised by an indurated discolouration of the skin ¹.

Microscopic appearance

Microscopic characteristics of retiform haemangioendotheliomas include the following ¹:

• reticulated, net-like pattern of narrow elongated vascular channels similar to the rete testis

• monomorphic hyperchromatic endothelial cells with scant cytoplasm and hobnail appearance

• rare mitotic activity 

• absent pleomorphism

Immunophenotype

Immunohistochemistry stains usually react to vascular markers such as CD31, CD34, ERG or factor VIII-related antigen ^1,4. The lymphatic marker PROX1 is usually positive whereas other lymphatic markers such as podoplanin and VEGFR3 are usually negative ¹.

Radiographic features

Since those tumours are very rare and usually affect the skin and the subcutaneous tissue, imaging plays a rather small role in their diagnosis and any reports of imaging appearances are scarce in the literature.

CT

Examples of retiform haemangioendotheliomas of the mediastinum and the neck showed heterogeneously enhancing soft tissue masses ^5,6.

Angiography (DSA)

Another report described focally increased vascularity during the capillary phase during angiography ⁴. 

Radiology report

The radiological report should include a description of the following:

• location and size

• distance from the muscular fascia

• regional lymph node involvement

Treatment and prognosis

Management includes local excision. Multiple recurrences even over long periods are common. Lymph node metastases or regional soft tissue metastases occur very rarely. Distant metastases or deaths due to the disease have not been described as yet ¹.

History and etymology

Retiform haemangioendotheliomas were first described by the British pathologists, Eduardo Calonje, Christopher D. Fletcher, Edward Wilson-Jones and the Italian-American pathologist Juan Rosai ².

Differential diagnosis

Conditions or tumours which can mimic the presentation and/or the appearance of retiform haemangioendotheliomas include:

• angiosarcoma

• haemangiomas e.g. hobnail haemangioma

• venous malformations