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Category: Canine
Hemangiosarcoma (HSA) is a cancerous tumor that arises in the lining cells of blood vessels. In dogs, it may develop as a primary tumor in the spleen, liver, heart, lungs, kidneys, and skin, as well as in other tissues. The most common location in dogs is the spleen. Hemangiosarcoma generally occurs in older, large breed dogs. The German shepherd is the most frequently affected breed.
Splenic hemangiosarcoma is a rapidly growing tumor that metastasizes (spreads) quickly. Spread of this cancer is facilitated by the vascularity of the spleen. Disruption of the spleen's vascular network by the growing tumor causes bleeding into the abdominal cavity (hemoperitoneum). The abdomen becomes distended as a result. The tumor mass also disrupts the normal functioning of the spleen. The spleen normally removes old, broken down red blood cells from circulation. Veterinarians feel that the resulting increased numbers of these circulating fragments cause disseminated intravascular coagulation (DIC), which is the abnormal clotting of the smallest blood vessels. This clotting in turn may lead to dysfunction of other tissues.
Blood loss from the spleen results in anemia, which gives rise to important clinical signs. Dogs with splenic hemangiosarcoma may have pale mucous membranes, and experience loss of appetite and weakness. They may even collapse from shock or cardiac arrhythmias. The examining veterinarian may be able to palpate the enlarged spleen and the distended abdomen.
A complete blood count (CBC) will show decreased numbers of red blood cells. Examination of a blood sample under the microscope may reveal an increase in the number of immature red blood cells as further evidence of severe anemia. X-rays and abdominal ultrasonography may be helpful in revealing a splenic mass or peritoneal effusion, that when sampled, appears as nonclotting blood. Splenic masses may also be benign, as is the case with splenic hematomas. Definitive diagnosis requires a surgical biopsy. If there are multiple masses, suggesting spread to the liver or other organs, cancer may be the more likely diagnosis.
Initial treatment involves medical stabilization with fluids, possibly blood transfusions, then surgical excision of the spleen. There is substantial evidence that administering chemotherapy after surgery affords the longest survival times.
Generally, chemotherapy is started as soon as possible once the animal is stabilized and the veterinarian feels that it is appropriate. The starting time is also dependent on which drugs are chosen as part of the treatment plan. Recommended treatment protocols involve the use of doxorubicin as a single agent or in combination with cyclophosphamide or vincristine, and infrequently, methotrexate. There are biologic therapies available that according to preliminary data may improve survival time when added to chemotherapy.
The prognosis is poor for dogs with splenic and other non-cutaneous forms of hemangiosarcoma. Most dogs ideally treated surgically and with optimal combinations of chemotherapeutic and biologic agents will die within a year of discovery of the tumor. |