Endothelial lesions of soft tissues: a review of reactive and neoplastic entities with emphasis on low-grade malignant ("borderline") vascular tumors.

Soft tissue proliferations composed of endothelial cells are a heterogeneous group of lesions that can cause diagnostic difficulty. Further complicating the issue is the constantly changing nomenclature of some entities, as well as reclassification of some vascular tumors from the high-grade malignant category to the low-grade malignant or borderline category. Modern ancillary techniques such as immunohistochemistry and cytogenetics have done little to advance our knowledge of these lesions. This review article outlines the most recent classification of endothelial lesions of the skin and soft tissues, with emphasis on the low-grade malignant (borderline) category. In addition, many tumor-like lesions containing an endothelial component are also discussed.