Definition of Hemangiosarcoma
Hemangiosarcoma, also called angiosarcoma, hemangioendothelioma or HAS, comes from uncontrolled overgrowth of cells lining small blood vessels. What causes hemangiosarcoma in dogs is poorly understood, although genetics probably play a role. These are fast-growing, invasive, fragile tumors that can occur anywhere on or in a dog’s body and tend to spread rapidly. Hemangiosarcomas bleed profusely when disturbed and often rupture, causing life-threatening internal bleeding. Hemangiosarcomas seem to cause dogs a great deal of discomfort, especially in the later stages. The exact symptoms depend on where the original tumor is and where it has spread. Sometimes, the initial signs of hemangiosarcoma are chalked up to old age, changes in weather or alterations in the dog’s living environment. However, once the disease advances, most dogs deteriorate rapidly. Some die suddenly from internal bleeding if a tumor ruptures. Unfortunately, hemangiosarcoma is fairly common in dogs, especially in large and giant breeds.