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Retiform Haemangioendothelioma

Retiform haemangioendothelioma is a locally aggressive, rarely metastasizing vascular lesion, characterized by distinctive arborizing blood vessels lined by endothelial cells with characteristic hobnail morphology.

Symptoms & Causes

Introduction

Retiform haemangioendothelioma is a rare vascular tumor found in the skin and subcutaneous tissue, notable for its arborizing blood vessels and hobnail-shaped endothelial cells, usually non-metastatic but locally aggressive.

Reference
WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours [Internet]. Lyon (France): International Agency for Research on Cancer; 2020 [cited 2024 09 11]. (WHO classification of tumours series, 5th ed.; vol. 3). Available from: https://tumourclassification.iarc.who.int/chapters/33.

Related Terminology
Acceptable: hobnail haemangioendothelioma.

Subtype(s)
None

Symptoms

Retiform haemangioendothelioma presents as a red/bluish slow-growing plaque or nodule, usually < 3 cm in maximum dimension. A case with multiple lesions has been described. Exceptional cases occur in the setting of previous radiotherapy or pre-existing lymphoedema (including Milroy disease), as well as in association with a cystic lymphangioma.

Localization

The tumor involves predominantly the skin and subcutaneous tissue and is most commonly found in the distal extremities, particularly the lower limb.

Epidemiology

Retiform haemangioendothelioma is uncommon. Since its original description in 1994, only about 40 cases have been reported. The age range is wide, but this lesion usually affects young adults or children; males and females are affected equally frequently.

Etiology

Unknown

Diagnosis & Treatment

Staging

Not clinically relevant

Pathogenesis

Unknown

Macroscopic Appearance

Macroscopic examination reveals diffuse, sometimes discolored induration of the dermis, with frequent involvement of the underlying subcutaneous tissue.

Histopathology

Scanning magnification reveals characteristic elongated and narrow arborizing vascular channels with a striking resemblance to normal rete testis. Although this pattern is usually readily apparent, if the vascular channels are small or collapsed, then the retiform architecture may be difficult to recognize. Monomorphic hyperchromatic endothelial cells with prominent protuberant nuclei having a characteristic tombstone or hobnail appearance line the blood vessels. These cells have scant cytoplasm, which seems to blend with the underlying stroma. Pleomorphism is absent and mitotic figures are rare. A prominent stromal and often intravascular lymphocytic infiltrate is present in about half of the cases. The stroma surrounding the tumor tends to be sclerotic. Focal solid areas composed of sheets of endothelial cells are often identified. Vacuolated cells are uncommonly seen. Monomorphic endothelial spindle-shaped cells are also a rare feature and were described in a case of metastatic disease in a lymph node. In some cases, there are intravascular papillae with hyaline collagenous cores similar to those seen in papillary intralymphatic angioendothelioma. Retiform haemangioendothelioma can be one of the components of a composite haemangioendothelioma. The neoplastic cells in retiform haemangioendothelioma stain for vascular markers, including CD31, CD34, and ERG. Staining for CD34 is often stronger than for other vascular markers. Although the lymphatic marker PROX1 is positive in retiform haemangioendothelioma, other lymphatic markers, including podoplanin (D2-40) and the less specific VEGFR3, are usually (but not always) negative. These lesions are negative for HHV8.

Cytology

Not clinically relevant

Prognosis and Prediction

Multiple local recurrences (occurring in as many as 60% of cases), often over many years, are the rule, unless wide local excision is performed. Very rarely, lymph node or locoregional soft tissue metastasis may occur. To date, no patients have developed distant metastases or died from this disease.

Clinical Features

Diagnostic Molecular Pathology

Not clinically relevant

Essential and Desirable Diagnostic Criteria

Essential: arborizing branching vascular channels; bland endothelial cells with hobnail morphology and no or very low mitotic activity.

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