Hemangiosarcoma is a relatively common type of cancer that forms from the cells that line blood vessels. The tumors are often located in the spleen, heart or under the skin and are most frequently diagnosed in middle-aged or older, large breed dogs.




Symptoms associated with a hemangiosarcoma depend on its location. The tumors frequently bleed, which can lead to weakness, pale mucous membranes and collapse. Bleeding from the spleen may produce a pot-bellied appearance as blood collects in the abdomen. Bleeding from cardiac tumors collects within the sac that surrounds the heart and compromises heart function. Hemangiosarcomas that lie just under the skin look like a red colored mass or a bruise. A veterinarian will often make a tentative diagnosis of hemangiosarcoma based on an animal's age, clinical signs and the discovery of a tumor and/or bleeding in a typical location. To definitively differentiate hemangiosarcomas from other masses that can cause similar clinical signs, a veterinarian will need to send a tissue sample to a pathologist for identification.




Dogs with internal hemangiosarcomas are often in critical condition when they are brought to the veterinarian. Transfusions may be necessary, and in the case of cardiac tumors, blood may need to be removed from the space around heart. Once the animal is stable, surgery is necessary to either take out the spleen or to remove as much of the mass from the heart as possible and to provide a way for blood to drain out of the sac that surrounds it. In the majority of cases, internal hemangiosarcomas have already spread to other parts of the body at the time of diagnosis. Chemotherapy after surgery can extend an animal's life, but long-term survival rates are low. Hemangiosarcomas that involve the skin carry a better prognosis when they are identified early and can be completely removed.


Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008