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Hemangiosarcoma is a malignant tumor that arises out of the cells of the blood vessels, and therefore can technically grow out of any tissues rich in blood vessels. Hemangiosarcoma occurs in both dogs and cats, but tends to be significantly more common in dogs, with generally different tissue predispositions unique to each species.


In dogs, hemangiosarcoma most commonly presents from the spleen, the skin, or the heart base. Sometimes, multiple forms are present at once, as evidenced in the fact that about 25% of patients with splenic hemangiosarcomas also have heart base hemangiosarcomas.

Hemangiosarcoma of the Spleen

Tumors of the spleen in the canine are often difficult to detect early or even mid-stage, since the spleen is a deep seated abdominal organ. Most early diagnoses of splenic hemangiosarcome in dogs are found incidentally when imaging of the abdomen is performed on routine screening or looking for other diseases of the abdomen. Once splenic hemangiosarcomas are discovered on physical examination or through other diagnostics because the patient is clinically sick, prognosis tends to be guarded to poor. Hemangiosarcomas of the spleen high a high tendency to bleed, making severe, life threatening anemia from internal bleeding a common emergency presentation.

Surgery (removal of the spleen known as splenectomy) alone offers a survival time of 2-4 months, with surgery combined with chemotherapy increasing survival time to about 5-7 months.

Hemangiosarcoma of the Heart Base

Hemangiosarcomas of the heart base occur primarily, but in dogs are also often the result of metastasis from primary splenic hemagiosarcoma (25% of cases of canine hemangiosarcoma of the spleen also present with heart base hemangiosarcoma). Like hemangiosarcoma of the spleen, heart base hemangiosarcomas also have a high potential to bleed making hemorrhage into the sac surrounding the heart, called the pericardium, a dangerous complication. When this type of hemorrhage occurs, the blood fills up the pericardium until it is so full that the heart inside is under so much pressure that it has no room to fill with the blood it has to pump, a circulatory system compromise known as pericardial tamponade.

If a patient presents with pericardial tamponade, the pressure needs to be relieved by using ultrasound to guide a needle into the pericardium and aspirate out the blood. Treatment for heart base hemangiosarcoma is the same as for splenic hemangiosarcoma, which consists of surgery alone or surgery combined with chemotherapy. Survival time with surgery alone versus surgery combined with chemotherapy is comparable to hemangiosarcoma of the spleen.

Cutaneous Hemangiosarcoma

Cutaneous hemangiosarcoma or hemangiosarcoma of the skin tends to be aggressive, with about 60-70% of cases having spread to internal tissues by the time of diagnosis. Therefore, in cases of cutaneous hemangiosarcoma it is just as important as other forms to rule out other forms of hemangiosarcoma to determine prognosis and the best treatment course. Again, regarding treatment for canine cutaneous hemangiosarcoma, survival time with surgery alone versus surgery combined with chemotherapy is comparable to the other forms of the disease.


Hemangiosarcomas in cats overall are substantially less common than in dogs. However, hemangiosarcoma still can occur in felines, with the most common sites tending to be:

Cutaneous (under the skin)
Visceral (involving internal organs)
Oral (usually growing from the gums)

Cutaneous hemangiosarcomas tend to occur most commonly on the head in cats, indicating that sun exposure contributes ot the overall risk of these tumors. If diagnosed early enough for complete surgical excision, surgery alone tends to be curative with clean surgical margins, given these tumors’ low tendency to spread internally. Visceral hemangiosarcoma carry a very poor to grave prognosis with many cats undergoing euthanasia due to such severe systemic compromise at the time to diagnosis.

Roger L. Welton, DVM
Founder and Chief Editor,
President, Maybeck Animal Hospital

Article updated 10/30/2012

2 thoughts on “Hemangiosarcoma

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