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Vascular Malformations at a Glance
  • Worldwide prevalence: roughly 0.3%.
  • Congenital, diversified but localized and well-demarcated lesions of malformed vessels of various types: capillary, venous, lymphatic, and arteriovenous.
  • Histologically consist of enlarged, tortuous vessels of various types.
  • Can be isolated, combined, or part of a syndrome.
  • Management: multidisciplinary approach.

Vascular malformations are believed to be due to errors of development of vessels that occur during the fourth and tenth weeks of intrauterine life. Most vascular malformations are sporadic, although several families with inherited forms have been identified. They are very heterogeneous and affect about 0.3% of the population. Vascular malformations are mostly congenital, even if they may be diagnosed only later in life.

Although several genes have been identified as the cause of inherited forms of vascular malformations, the etiology of the most common sporadic lesions is unknown.13 Histologically, vascular malformations consist of enlarged, tortuous vessels with quiescent endothelium. In contrast to hemangioma, there is neither parenchymal mass nor cellular proliferation.

For many years, vascular anomalies were grouped under the term angioma, hampering precise classification and leading to incorrect diagnosis and improper management. For example, the term hemangioma has been used both for vascular malformations, often of venous type (cavernous hemangioma) as well as for vascular tumors (strawberry hemangioma). This nomenclature changed in 1982 with the development of a biologic classification by Mulliken and Glowacki. It divided vascular anomalies into two major categories: (1) vascular tumors (with cellular proliferation; hemangioma being the most common) (see Chapter 126), and (2) vascular malformations (structural anomalies of blood vessels) that are subsequently subdivided, depending on the affected vessel type, into arterial, capillary, lymphatic, or venous malformations.4,5 In 1996, this classification was adopted and further developed by the International Society for the Study of Vascular Anomalies (ISSVA) (Table 172-1).6 Vascular malformations mostly affect only one vessel type, yet combined malformations also exist. They are named according to the affected vessel types, (e.g., capillary-venous or venolymphatic malformation). In addition to isolated forms, vascular malformations occur in syndromes such as Klippel–Trenaunay (KT) (capillary-lymphaticovenous malformation with limb hypertrophy), Maffucci syndrome (multiple enchondromas associated with multiple venous anomalies and high incidence of malignancy)7, Cloves syndrome (congenital lipomatous overgrowth with vascular malformations, epidermal nevi, and scoliosis)8,9, or Parkes Weber syndrome (high-flow vascular malformation of the extremity with soft tissue hypertrophy).10

Table 172-1 Classification of Vascular Tumors and Malformations

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