Retiform hemangioendotheliomas or hobnail hemangioendotheliomas are intermediate locally aggressive and rarely metastasizing vascular neoplasms with a distinctive hobnail endothelial cell morphology.
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Epidemiology
Retiform hemangioendotheliomas 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
lymphedema including Milroy disease
Diagnosis
The diagnosis of retiform hemangioendothelioma is established histologically.
Diagnostic criteria
Diagnostic criteria according to WHO classification of soft tissue and bone tumors (5th 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 hemangioendotheliomas usually appear as slow-growing, red-colored bluish skin lesions. They have been described as soft and compressible and are usually smaller than 3 cm upon diagnosis 1,4.
Pathology
Retiform hemangioendotheliomas are characterized by a distinctive hobnail endothelial cell morphology and a typical branching, arborizing vascular pattern 1.
Etiology
At the time of writing the etiology of retiform hemangioendotheliomas remains unknown 1.
Location
Retiform hemangioendotheliomas usually affect the dermis and subcutaneous tissue of the distal extremities, especially the lower limb 1.
Macroscopic appearance
Macroscopically retiform hemangioendotheliomas are sometimes characterized by an indurated discolouration of the skin 1.
Microscopic appearance
Microscopic characteristics of retiform hemangioendotheliomas 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 tumors 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 hemangioendotheliomas 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 hemangioendotheliomas 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 tumors which can mimic the presentation and/or the appearance of retiform hemangioendotheliomas include:
hemangiomas e.g. hobnail hemangioma