[Hemangioendotheliomas--evolution of a concept of a heterogeneous group of vascular neoplasms]

The term haemangioendothelioma has been used in the past for a number of vascular lesions, which vary not only by their morphological features, but more importantly, also by their biological behavior. In the recent WHO-classification of mesenchymal tumours haemangioendotheliomas have been defined as vascular tumours of "intermediate" or "borderline" malignancy, and spindle cell haemangioendothelioma (SHE), epithelioid haemangioendothelioma (EHE), and rare malignant endovascular papillary angioendothelioma (Dabska's tumour) were included in this category. To this list might be added the more recently delineated kaposiform (KHE), retiform (RHE), polymorphous (PHE), and composite haemangioendothelioma (CHE). Although very popular, the concept of "borderline" or "intermediate" malignancy encompasses a wide variety of clinical situations, prognosis, and biological behavior. Therefore uncritical use of the term haemangioendothelioma represents a potential source of confusion to patients and oncologists, and it should not be used without further clarification. SHE was originally described as low-grade angiosarcoma, however, the study of large series with expanded follow-up information clarified that these lesions are often multicentric in one anatomic region, whereas true recurrences are rather rare, and systemic metastases and tumour progression do not occur. Therefore redesignation of these lesions as spindle cell haemangioma has been proposed. EHE of skin and soft tissues represents a distinctive vascular neoplasm characterized by nests and cords of epithelioid endothelial tumour cells with characteristic cytoplasmic vacuoles, which are set in a myxohyaline matrix. The reported rates of systemic metastases (20-30%), and tumour related death of patients (13-17%) in EHE, and the occurrence of multicentric EHE argue against the classification of EHE as a low-grade or "borderline" malignant neoplasm; EHE should be better regarded as a clearly malignant vascular tumour (G2). Although it seems that KHE is associated with a high mortality rate, the deaths are almost always related to locally invasive effects or as result of bleeding and consumption coagulopathy. So far no metastasizing case of KHE has been reported, and it seems that the prognosis in KHE is mainly related to size, anatomical site and depth of the lesion. KHE should be classified as a locally aggressive, non-metastasizing vascular tumour. The remaining entities (RHE, Dabska's tumour, PHE, and CHE) are characterized by an infiltrative growth, a high rate of (often repeated) local recurrences, and a definitive risk of metastases. Therefore these lesions fulfil criteria for low-grade malignant vascular neoplasms.