II. INTRODUCTION
The International Society for the Study of Vascular Anomalies (ISSVA) initially proposed, and continues to update, a widely held classification system for approaching vascular anomalies. There are two broad general groups: 1) tumors (which are proliferative in nature) and 2) malformations (which are non-proliferative in nature). Simple malformations refer to capillary (CM), lymphatic (LM), venous (VM), or arteriovenous malformations (AVM) (1). Malformations can be localized to a specific body area, or more extensive in nature. Vascular malformations are thought to arise from somatic mutations acquired during fetal development (2). Most will present at birth or in early childhood (3). They exhibit a wide variability of clinical impact ranging from asymptomatic lesions, to cosmetic concerns, and even life-threatening symptoms due to close proximity to vital structures such as the airway or lungs (4,5). In general, clinical evaluation and imaging is usually diagnostic, but occasionally biopsy is needed if atypical features are present. Biopsy is not without risk, as lesions are prone to bleed. Immuno-histochemical markers and examination of vascular architecture can clarify diagnosis. CD34 confirms endothelial origin (6), while D2-40 (podoplanin) and LYVE-1 are associated with lymphatic vessels. CD31 and SMA stain positive in VMs (7). Genetic analysis of tissue will become more important as options for targeted therapy become increasingly available. In this review, we describe four cases and examine the clinical features, diagnostic options, and management strategies of simple, localized malformations. As a multi-disciplinary team is often needed to manage these complex patients, we will examine the role of multiple disciplines, including the pediatric hematologist and oncologist, in the care of patients with vascular malformations.