Hamburg classification system of vascular malformations
Hamburg classification system of vascular malformations is one of the more commonly used systems to describe the wide range of vascular malformations, largely replacing the many various eponymous syndromes traditionally used. It accounts for the underlying anatomical, histological, and pathophysiological features of congenital vascular malformations (CVM) . It also introduces embryological aspects, further subdividing them into either an extratruncular or truncular form, based on the time of developmental arrest during embryonic life .
The other frequently used system is that proposed by Mulliken and Glowacki, now adopted by the International Society for the Study of Vascular Anomalies (ISSVA) (see ISSVA classification of vascular anomalies).
Truncular versus extratruncular
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 hemodynamic 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 “hemolymphatic 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.