Hemangiosarcoma in Dogs

What is hemangiosarcoma?

Hemangiosarcoma (HSA) is a malignant tumor of the cells that line blood vessels. It is much more common in large breed dogs, especially German shepards, Labrador retrievers and Golden retrievers. The primary site is usually the spleen. Other sites include the liver, heart, kidneys, bladder, muscle and subcutaneous tissues. HSA is a very aggressive cancer, with high potential for wide spread and early metastasis to other tissues such as the liver, lungs and peritoneum. The cause of HSA is unknown.

What are the symptoms?

Clinical signs of HSA are often related to rupture and hemorrhage of the tumor including:

  • Weakness (it can be intermittent)
  • Abdominal distension
  • Pale mucous membranes
  • Collapse

Dogs with tumors involving the right atrium of the heart may present with:

  • Arrhythmias
  • Muffled heart sounds
  • Signs of heart failure

Some dogs may suffer sudden death due to a rupture of a mass in a critical location or severe and acute blood loss into a body cavity.

HSA may occur as cutaneous, subcutaneous or deep masses invading or originating from the muscle. These locations may cause lameness, a hard swelling within the muscle or edema of the affected region.

How is it diagnosed?

Many dogs with the splenic form of HSA will present to the veterinarian for rupture of the tumor and bleeding within the abdomen. The following diagnostics are recommended:

  • Abdominal tap
  • Abdominal ultrasound
  • Radiographs
  • Aspirates and biopsies of splenic masses
  • Blood work

Surgical removal of the spleen (splenectomy) and associated masses with histological evaluation is necessary for diagnosis.

An echocardiogram may be recommended to evaluate for heart masses. Approximately 10-20% of dogs with splenic HSA will have right atrial involvement.

How is it treated?

Surgery remains the primary method of treatment of HSA. Typically chemotherapy is recommended in conjunction with surgery, however, while it may extend disease-free intervals, long-term control rates remain very low. Very few studies have been conducted to evaluate immunologic or biologic therapy in HSA. Palliative radiation therapy may help decrease symptoms of external masses, but will not impact disease at other sites.

What is the prognosis?

The median survival times with surgery alone range between 30 to 120 days. The addition of chemotherapy may double survival times. Although survival times are short, the quality of your pet’s life during this time should be excellent. New treatment options are constantly being explored.

Cutaneous HSA with invasion into subcutaneous areas or muscle have an average survival time between 6-11 months. Invasive cutaneous tumors warrant adjuvant chemotherapy.

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