Classification of congenital vascular malformations

Congenital vascular malformations (CVMs) are a heterogeneous group of rare dysplasias that may affect the arterial, capillary, venous or lymphatic system or any combination thereof. They are present at birth, may increase in size and, other than infantile haemangiomas, do not regress spontaneously. Traditional denominators like F.P. Weber and Klippel-Trénaunay syndromes have become obsolete in times of modern vascular imaging. Modern treatment options in different types of malformations require a more accurate description of the affected vascular components and the ensuing haemodynamic effects.

Classification systems

Mulliken and Glowacki system

Simple malformations

• slow flow
  • capillary
  • lymphatic
  • venous
• fast flow

  • arterial 

    • aneurysm
    • coarctation
    • ectasia
  • arteriovenous fistulae (with one ore more shunts)
  • arteriovenous malformations (with a nidus of multiple shunts)

Complex malformations

• regional
  • Sturge-Weber syndrome
  • Klippel-Trénaunay syndrome
  • F. P. Weber syndrome
• diffuse
  • Maffucci syndrome
  • Solomon syndrome
  • Proteus syndrome

Traditional eponyms still form a substantial part of this first comprehensive CVM classification system¹. Its advantage is that it includes all types of vascular anomalies and further classifies CVMs as ‘fast flow’ and ‘slow flow’ lesions based on conventional angiographic findings, which may be useful for the appropriate choice of therapy. However, it still lacks enough detail to form the base for the clinical management of certain types of CVMs and its combination with the traditional eponyms remains a source of confusion².

Hamburg classification system (see diagram)

The role of eponyms has been largely replaced by the newer Hamburg classification³. The Hamburg system accounts for the underlying anatomical, histological, and pathophysiological features of CVMs. It also introduces embryological aspects, further subdividing them into either an extratruncular or truncular form, based on the time of developmental arrest during embryonic life⁴.

Truncular versus extra-truncular

Extratruncular forms of CVMs arise early in embryonic life, while the vascular system is still in the reticular stage. They are in fact mesodermal tissue remnants, that retain the potential of angioblasts to grow and proliferate when stimulated. This is why these lesions may continue to grow and carry a significant risk of a recurrence after therapeutic interventions.

Truncular forms of CVMs arise at a later stage, when developmental arrest occurs during the vascular trunk formation. Truncular lesions have lost the potential to grow and proliferate. Thus, they carry only a minimal risk of recurrence. However, they are often associated with more serious haemodynamic consequences. Truncular lesions are further subdivided into obstructive or dilatative lesions. They present as various degrees of developmental defects of a vascular trunk, which may include agenesis or aplasia on the one hand and aneurysms or persistent embryonic channels on the other.

The vascular components of Klippel–Trénaunay syndrome (KTS) and F. P. Weber syndrome (FPWS) have been well defined as “haemolymphatic malformations” using the Hamburg classification system. The CVM in KTS includes venous, lymphatic and capillary components, while the hallmark of FPWS is arteriovenous shunting, mainly combined with capillary malformations. The Hamburg classification is nowadays the most accepted classification system among vascular surgeons. It is subject to continual improvement by the International Society for the Study of Vascular Anomalies (ISSVA)^2,4.