Venous malformations are made up of abnormally enlarged veins. They will gradually expand or grow over time as the walls of the veins stretch, causing swelling, and sometimes pain. As blood remains in the vein, the vein will enlarge. Because the blood moves slowly, there is a chance that clots will form and may calcify.
Arteriovenous Malformations are always present at birth but are usually not noticed until later in life. Sometimes they do not appear until adulthood. Defective blood flow has been associated with these lesions. As the lesion ages, the vessels enlarge and thicken to compensate for the increased blood supply. There are two grades: low and high. Low grade grow slowly with the child and high grade expand rapidly, growing faster than the child until the lesion may eventually become life threatening.
An AV malformation is a firm mass. Common sites are the lips and other head and neck areas. Mixed malformations include a combination of two or more vascular lesions.