What is it?

Hemangiosarcoma is a form of cancer originating in the endothelium which occurs more frequently in dogs than in any other species.

Because hemangiosarcomas start in the blood system, and because blood vessels are necessary in almost all body tissues, they are highly malignant and can travel to almost any part of the body. The spleen, heart and pericardium are most often affected, with the liver and skin being less often involved. This type of cancer tries to build blood vessels in a haphazard fashion which essentially causes blood blisters to form and disrupts normal organ function. The blood blisters also rupture easily causing bleeding from the cancer sites.

This is a highly malignant type of cancer, and an extremely metatastic one. Almost all dogs diagnosed with hemangiosarcoma will develop metastases within six months of their being diagnosed. The most common place for hemangiosarcoma to metastasise to is the brain, but it can also spread to the lungs, liver, spleen, heart, kidneys, skeletal muscle and bone

On examination,  the tumour can be of varying sizes (sometimes weighing as much as ten or more pounds when they affect the spleen) and can be coloured pale grey through to dark red. They are nodular in form and soft to touch. Because these tumours can rupture within the body, when examined they may have visible signs of these ruptures and of necrosis.

Hemangiosarcomas are poorly-formed, non-encapsulated and often adhere to adjacent organs.

Who Gets it?

Older dogs (over six years of ages) of larger breeds are affected by hemangiosarcoma more than any other dogs. Within that grouping, German Shepherds, Golden Retrievers and black dogs of any breed get hemangiosarcoma more often than other types.  More male than female dogs are affected.

My vet tells me that German Shepherds and Black dogs make up more than 90% of her patients with hemangiosarcoma. 

What are the symptoms?

Most commonly, the families of dogs affected by hemangiosarcoma will not be aware of any great problem until the disease has progressed too far to be successfully treated. The dog will seem well (particularly if the primary site is the spleen) until the tumour ruptures. If this rupture is slight, the dog may seem very tired and will have very pale gums and eyelids. If the rupture is more severe, the dog may simply die.

Some symptoms which may occur are:


Any tumour in the spleen or heart, particularly in a larger, older dog, will make the veterinarian highly suspicious of the presence of hemangiosarcoma. He will check the dog for signs of anemia (pale gums and eyelids) and need to be told how the dog has been behaving in the last few days or weeks.

Often, he will take an x-ray or ultrasound of the dog and order other tests with can include:

Diagnosis is accomplished by biopsy or removal of the tumor. This can be difficult because there may be multiple tumors present, the primary tumor site may prove challenging to determine, and there is great risk of severe hemorrhage.

Tumours on the spleen and even on the heart may be possible to remove while they are small. In some cases this will prolong the dog's comfortable life, but often by the time the tumours are discovered it is too late for this to be of much help.

No hemotheraputic or radiation treatments have been found to be very effective on this type of cancer as yet, although some dogs treated with chemotherapy and drugs including cyclophosphamide, vincristine, doxorubicin and cytoxan do live a little longer than those who are not.


Long-term prognosis of dogs with hemangiosarcoma is poor.

Studies have shown that surgery alone, usually a splenectomy, offers a median survival time of 19-83 days.

Dogs with splenic tumours which have ruptured generally live a shorter time than this.

A combination of splenectomy and chemotherapy can increase survival time up to a year in less than 10% of cases.

Quick Facts


  •  43% of dogs with splenic masses have hemangiosarcoma (HSA)
  • 50% of dogs with splenic HSA are in DIC at presentation
  • Average post-splenectomy survival times reported are: 49-120 days
  • Liver biopsy is essential to differentiate between liver metastasis and benign hyperplasia
  • Shepherds and northern breeds are at increased risk for developing HSA
  • Stage I cutaneous HSA can be cured with aggressive surgical resection
  • Three views of the lungs are required to rule out pulmonary metastasis
  • Cardiac HSA is the most common cause of pericardial effusion in dogs.
  • Chemotherapy significantly increases average survival time in dogs with cardiac HSA
  • HSA in cats is rare but occurs most commonly within the abdomen or subcutaneous tissue

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