Although this tumor can arise in any tissue, such as the heart, liver, brain and subcutaneous tissues, the spleen is the most common site. Hemangiosarcomas are by nature aggressive, highly metastatic and associated with a relatively poor prognosis.
Affected dogs are often older large-breeds and usually present with a brief history of lethargy, collapse (if splenic rupture has occurred), anemia, weight loss and intermittent anorexia, and are often diagnosed relatively late in the course of the disease.
Cutaneous hemangiosarcomas are the least metastatic and are associated with ultraviolet light exposure in dogs and often arise on the ventral abdomen and prepuce, where the hair coat is sparse. Lingual hemangiosarcomas have also been reported, with a similar nature and metastatic rate to cutaneous hemagniosarcomas.
Diagnosis is usually based on presenting clinical signs supported by radiographic and ultrasonographic identification of organomegaly or an abdominal mass. Staging of hemangiosarcomas on histological appearance is not usually reflective of survival time.
Hematology usually reveals varying degrees of thrombocytopenia, prolonged activated partial thromboplastin time, regenerative anemia and reticulocytosis. DIC may occur in up to 30% of affected dogs.
Definitive diagnosis requires histopathological analysis of splenic or other affected visceral organs, where hemangiosarcomas have a characteristic appearance with vascular spaces lined by elongated, plump, anaplastic endothelial cells. The nuclei are large and hyperchromatic, and mitotic figures are often seen. Bone marrow biopsies are usually recommended if myelodysplasia is apparent from blood tests.
Treatment is usually limited to surgical removal of devitalised tissue, splenectomy and debulking of tissue, but metastases are often present, warranting a more conservative approach in most cases.
Cutaneous hemangiosarcomas can be successfully removed surgically with wide margins of excision. However, all primary locations except superficial cutaneous tumors have a poor long-term prognosis and surgery is only for palliative purposes in most instances.
Chemotherapy should be considered the primary treatment. Doxorubicin is the recommended drug of choice in combination with vincristine and cyclophosphamide. A multidrug DAV protocol (doxorubicin, dacarbazine and vincristine combination) has shown promise, where doxorubicin and dacarbazine are administered on day 1 while vincristine is administered on days 8 and 15, with the protocol repeated every 21 days for a maximum of six cycles or until disease progression. This regimen has shown efficacious (50% response rate; 125 day survival) against canine hemangiosarcoma.
The prognosis for patients with splenic hemangiosarcoma is poor despite aggressive surgery and chemotherapy, with survival times from a few weeks to 6 months in most cases.
Cutaneous hemangiosarcomas have a better prognosis of 1 - 2 years.
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