Retiform hemangioendothelioma

Last revised by Henry Knipe on 25 Oct 2022

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

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.

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

The diagnosis of retiform hemangioendothelioma is established histologically.

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

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.

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

At the time of writing the etiology of retiform hemangioendotheliomas remains unknown 1.

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

Macroscopically retiform hemangioendotheliomas are sometimes characterized by an indurated discolouration of the skin 1.

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

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.

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.

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

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

The radiological report should include a description of the following:

  • location and size

  • distance from the muscular fascia

  • regional lymph node involvement

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.

Retiform hemangioendotheliomas were first described by the British pathologists, Eduardo CalonjeChristopher D. FletcherEdward Wilson-Jones and the Italian-American pathologist Juan Rosai 2.

Conditions or tumors which can mimic the presentation and/or the appearance of retiform hemangioendotheliomas include:

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