Angiosarcoma is a rare tumor of the endothelial (blood vessel) cells encountered mostly in adults (2 cases per million people per year). In children, it is extremely rare, and may arise on the skin or in different organs of the body. In some cases, angiosarcoma may arise from previously existing hemangioma. It is a very aggressive tumor, and can spread rapidly to the lungs and liver. With the current treatment regimens, the prognosis for patients with angiosarcoma, both children and adults, is very poor. The two other vascular cancers, lymphangiosarcoma and epithelioid hemangioendothelioma, have an even lower incidence.

Often the symptoms of vascular cancers are nonspecific, and are related to the location of the tumor. The accurate diagnosis of these tumors by microscopic evaluation of a tumor biopsy may be difficult even for an experienced pathologist. Therefore, by the time the condition is identified, the tumor may have widely spread, and challenging to cure. There are no consensus guidelines for treatment of vascular cancers in children, and most physicians follow adult protocols. The North American Pediatric Angiosarcoma Registry was established to optimize the diagnosis and treatment of vascular cancers in children.