Terminology and classification of congenital vascular malformations.

Venous malformation (VM) is a congenital vascular malformation (CVM) that develops along the venous system through the various stages of embryogenesis. Older terminology and classification were often misleading and confusing. A newer classification system has emerged that is based on advances in the study of these conditions and is useful in contemporary management. The Hamburg classification was introduced after reappraisal of older terminology and has become the standard system for contemporary classification, which is based on anatomical, pathological and embryological criteria.