Marginal vein is not a varicose vein; it is a venous malformation

Marginal vein (MV) is one form of venous malformation (VM); MV is not a varicose vein. MV is the outcome of defective development during the later stage of embryogenesis while the vein trunk is formed. It is an embryonic vein tissue remnant remaining on birth following the failure of normal involutional process. MV is the most common VM involved to Klippel-Trenaunay syndrome (KTS); together with the lymphatic malformation, MV is one of two clinically most important congenital vascular malformation components among KTS. MV causes chronic venous insufficiency (CVI) due to a unique condition of avalvulosis (lack of venous valve development) it accompanies with. Besides, it accompanies a high risk of venous thromboembolism (VTE) due to its structural defect with a lack of smooth muscle cell to form the media properly as a truncular VM infrequently causing fatal pulmonary embolism. Therefore, the MV is indicated for the surgical excision whenever feasible not only for the prevention of VTE and CVI but also for abnormal long bone growth known as vascular bone syndrome as well as lymphatic complication precipitated by MV.