Vascular malformations “of major named vessels” usually affect certain large-caliber arterial, venous or lymphatic vessels, most of them stem vessels or central conducting vessels. The involved anomaly is further classified according to vessel appearance (dilated, aneurysmal, stenotic, regarding a valve, etc.). This classification was introduced during the last revision of the ISSVA classification in 2014 and is less commonly used, as it is somewhat redundant compared to the simple malformations subgroup. It includes vascular dysplasia of vessels that are already relatively mature. These vessels have already matured as “tubes”. They are often significantly enlarged, and are comparable to similar non-dysplastic vessels with anatomically assignable names (thus “named vessels”). It is assumed that the development of the anomaly/dysplasia starts later in the development of these vessels and the malformed vessels are more mature overall. A characteristic example of this group is the marginal vein in Klippel-Trénaunay syndrome, a malformed, persistent embryonic vein that runs laterally along the lower extremity.
Vascular malformations “of major named vessels” represent those malformations of recognizable vessels that can be differentiated according to morphological criteria, i.e., based on origin, course, length and diameter. The following table systematically summarizes the vessels affected by vascular malformations in this subclassification and their underlying anomalies. In practice, this subclassification is rarely used because it redundantly reproduces some nomenclature that actually exists, but subdivides it more subtly.
|Affected vessel type||Morphological anomaly|
|Diameter (aplasia, hypoplasia, stenosis, ectasia, aneurysm)|
|Persistence of embryonic vessels|