CancerQuest | Canine Hemangiosarcoma

Cancer in Dogs

Introduction
Hemangiosarcoma (HSA) is a cancer that originates in cells that form blood vessels. HSA is responsible for approximately 7% of canine cancer cases. In fact, it is more common in dogs than any other species of animal examined!⁽¹⁾

HSA occurs most commonly in the spleen, skin, and the right atrium of the heart.⁽²⁾ Primary tumors have also been reported in the lung, aorta, kidney, oral cavity, muscle, bone, urinary bladder, prostate gland, vagina, lining of the abdominal cavity (peritoneum), intestine, tongue, and the membrane that covers the white part of the eye (conjunctiva).⁽³⁾ HSA is highly metastatic, meaning that it frequently spreads. When HSA is confined to the skin, it is less apt to spread. Veterinarians estimate that over 80% of all other cases have already metastasized at the time of diagnosis.⁽³⁾

HSA cells may release proteins that stimulate the growth of new blood vessels. This process is known as angiogenesis, and is critical for tumor formation. The presence of numerous blood vessels helps supply growing tumors with nutrients and oxygen and may serve as a "highway" for the cancer cells to metastasize to distant parts of the body.

Risk Factors
Older animals are at higher risk for developing hemangiosarcoma. Affected dogs are usually diagnosed between 9 and 12 years of age.⁽⁴⁾ HSA tends to affect large breed animals more often than smaller ones. Breeds that are more prone to this type of cancer include German Shepherds, Golden Retrievers, Labrador Retrievers, Pointers, Boxers, English Settlers, Great Danes, Poodles, and Siberian Huskies. Breeds with short hair, light hair, light skin, and/or less pigmentation (i.e. Whippets) are more prone to hemangiosarcoma of the skin⁽⁵⁾ ⁽³⁾ ⁽⁶⁾

Detection/Symptoms
Symptoms of HSA vary depending on the location and stage of the cancer, but may include weakness, weight loss, increased heart rate (tachycardia), abnormally fast breathing (tachypnea), abdominal swelling, lethargy, and paleness of mucous membranes. Episodes of acute weakness and/or collapse may indicate that a tumor has ruptured, causing uncontrolled blood loss. If internal bleeding occurs and the blood is reabsorbed from the body cavity back into blood vessels, the animal may gradually recover. In more severe cases, tumor rupture can cause sudden death.⁽³⁾

Veterinarians often detect HSA during physical examinations. They also use blood tests, urine analysis, chest x-rays, abdominal ultrasound, ultrasound of the heart (echocardiogram), tissue samples (biopsy), and more. One type of blood test, the complete blood count (CBC), can detect anemia, misshapen or fragmented red blood cells, and other signs of HSA. Some tests can even indicate the organ(s) being affected by the disease. A blood smear that shows an increased number of immature red blood cells (normoblasts) may indicate cancer of the spleen.⁽³⁾

Treatment
Surgery is the standard treatment for dogs with HSA. In one study, researchers from Colorado State University attempted surgery on 76 animals with HSA (66 dogs and 10 cats). In 42 cases, surgeons were able to remove the tumor(s) completely, leaving no visible cancer behind. Following surgery, all 42 of these animals remained healthy for at least 12 months. In the remaining 34 cases, the animals experienced incomplete tumor removal and/or other complications, resulting in worse clinical outcomes. These findings confirm that complete tumor removal is the most significant prognostic factor for this type of cancer. Researchers also found that certain tumors (i.e. eye or skin) were much easier to remove than others (i.e. bone or muscle).⁽⁷⁾

Veterinarians can use other methods to treat and manage hemangiosarcoma, but their effectiveness is limited. Chemotherapy can be used in addition to surgery. Research has shown doxorubicin to be the most effective chemotherapy drug for this type of cancer. Despite treatment, the survival time for HSA-affected dogs typically does not exceed 6 months. Death often results from metastasis to the lungs and other parts of the body.⁽¹⁾

References for this page:

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Pearson GR, Head KW. Malignant haemangioendothelioma (angiosarcoma) in the dog. Journal of Small Animal Practice (1976) 17: 737-745. [PUBMED]
"Canine Hemangiosarcoma." Department of Pathology. 2004. College of Veterinary Medicine, University of Georgia. 2 June. 2010. [http://www.vet.uga.edu/VPP/clerk/frankhauser/index.php]
Bertazzolo W, et. al. Canine angiosarcoma: cytologic, histologic, and immunohistochemical correlations. Veterinary Clinical Pathology (2005) 34(1): 28-34. [PUBMED]
Ward H, Fox LE, Calderwood-Mays MB, Hammer AS, Cuoto CG. Cutaneous hemangiosarcoma in 25 dogs: a retrospective study. J Vet Intern Med (1994) 8: 345-348. [PUBMED]
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