Vascular tumors are neoplasms of endothelial cell origin. These tumors comprise a broad and complex group of vascular anomalies. Diagnostic classification of these lesions is based on their unique clinical, radiologic imaging, histopathologic, and molecular characteristics. This article follows the published classification of the International Society for the Study of Vascular Anomalies. It describes characteristic histopathologic findings in vascular tumors and information on known genetic causes.