The term Hemangioendothelioma describes several types of vascular neosplasms and includes both non-cancerous (benign) and cancerous (malignant) growths. The term has also been applied to those that show "borderline" behavior, intermediate between entirely benign hemangiomas and highly malignant angiosarcomas. Hemangioendotheliomas are caused by abnormal growth of blood vessel cells, although the exact underlying cause for the abnormal growth is unknown. They can also develop in an organ, such as the liver or lung. They usually grow slowly and can sometimes spread to other tissues in the body (metastasize). Examples of types of Hemangioendotheliomas include spindle cell hemangioma; papillary intralymphatic (Dabska tumor); retiform; kaposiform; epithelioid; pseudomyogenic (epithelioid sarcoma-like Hemangioendothelioma); and composite.