A rare blood vessel tumor that usually forms on the skin of the arms and legs, but may also form in deeper tissues, such as muscle and bone. Kaposiform hemangioendotheliomas may sometimes form in the lymph nodes, chest, abdomen, or bones. They are fast growing and can spread to nearby tissue, but usually do not spread to other parts of the body. Signs and symptoms may include firm, painful areas of skin that look bruised; purple or brownish-red areas on the skin; easy bruising; anemia; and abnormal bleeding. Kaposiform hemangioendotheliomas are most common in infants and young children. They are a type of vascular tumor.