Hemangiosarcoma in Dogs

Tired Golden Retriever lying on wooden floor
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Hemangiosarcoma is a form of cancer that affects dogs more than humans or other animals. It can be a very serious form of cancer that spreads throughout the body quickly.

What is Hemangiosarcoma in Dogs?

Hemangiosarcoma is a cancer of the endothelial cells, which are the cells that line the interior of the blood vessels. Tumors are highly malignant and metastasis (spread to other parts of the body) may occur rapidly. Hemangiosarcoma growths can occur anywhere in the body, but most commonly occur in the spleen, liver, heart, and skin.

Tumors on the spleen have a tendency to bleed and may cause the abdominal cavity to fill with blood (hemoabdomen). Liver tumors usually have a similar effect.

Tumors in the heart most commonly appear in the right atrium and also tend to bleed. Blood fills up the sac around the heart (pericardium) and impairs cardiac function.

Hemangiosarcomas can also develop on the skin (dermal) or under the skin (subcutaneous). Dermal tumors are typically raised bumps that can be red, purple, and/or black. They may eventually ulcerate and bleed. Subcutaneous tumors are very malignant and likely to spread. Subcutaneous hemangiosarcoma may not be visible to the naked eye until it begins bleeding. This may look like a deep, spreading bruise.

Signs of Hemangiosarcoma in Dogs

Internal tumors (spleen, liver, heart) may not cause symptoms at first. Signs may appear vague at first and then suddenly get worse due to rupture and/or bleeding of the tumor. They can include:

  • Lethargy
  • Weakness (constant or intermittent)
  • Abdominal distension (bloated appearance of belly)
  • Pale gums and other mucous membranes
  • Collapse
  • Bruising, bleeding, lumpy or ulcerated skin

Causes of Hemangiosarcoma in Dogs

Hemangiosarcoma of the skin is typically caused by too much sun exposure. Tumors usually occur on hairless areas of the skin or areas with white hair.

The cause of internal hemangiosarcomas is not known. Any breed of dog can get this type of cancer. However, certain breeds appear to have a genetic predisposition. These include Golden Retrievers, German Shepherd Dogs, and Labrador Retrievers.

Hemangiosarcoma can affect dogs of any age, but it typically occurs in middle-aged and senior dogs.

Diagnosing Hemangiosarcoma in Dogs

Be sure to bring your dog to see the veterinarian if you notice skin bumps, symptoms of internal hemangiosarcoma, or any other signs of illness.

Your veterinarian will begin by discussing your dog's history and performing a full physical examination. Abdominal masses may or may not be palpable on examination. If there is blood or other fluid in your dog's abdomen, your vet might be able to feel it on the exam. Heart tumors may cause abnormal heart sounds that can be heard with a stethoscope.

The next diagnostic steps include full lab work (complete blood count, blood chemistry, urinalysis) and radiographs (X-rays) of the chest and abdomen. Your vet will be looking for lab abnormalities that can indicate cancer as well as visible tumors or abnormalities in the chest and abdomen.

Skin tumors can often be aspirated or biopsied. Samples are sent to a pathologist to look for microscopic cancer cells.

If a tumor is found internally, your vet may recommend an aspirate or biopsy if it is deemed safe for your dog. Cells from the tumor are collected with a needle and sent to a pathologist. If your dog has fluid in the abdomen, it may be collected and sent to a lab for analysis.

In some cases, a definitive diagnosis of hemangiosarcoma cannot be made until the tumor is surgically removed and sent to a pathologist.

Depending on the diagnosis, your primary veterinarian may refer you to a veterinary oncologist and/or veterinary surgeon for treatment.

Treatment of Hemangiosarcoma in Dogs

The first step to treat hemangiosarcoma in dogs is to surgically remove the primary tumor, if possible. Surgery for splenic tumors typically involves complete removal of the spleen (a dog can live without a spleen). Tumors that cannot be fully removed may be debulked as much as possible. Some tumors are inoperable, especially those in the heart.

Surgical removal of skin hemangiosarcomas is usually curative if the entire tumor is removed and there is no metastasis.

Staging is an important part of both the diagnostic and treatment process. Dogs will need full lab work, radiographs of the chest and abdomen, and possibly advanced imaging like CT or MRI. This allows the vet to see where in the body the cancer has spread and to then formulate the best possible treatment plan.

Chemotherapy is often recommended for dogs following surgery, especially if the mass could not be completely removed or if metastasis is present. A veterinary oncologist will develop a chemotherapy protocol that is best for your dog. This usually involves visits to the vet for chemotherapy injections every week or two for six months or longer.

Palliative radiation therapy may be recommended to reduce pain and provide a better quality of life when other treatments are not effective or if no other treatment options exist.

How to Prevent Hemangiosarcoma in Dogs

Hemangiosarcoma of the skin may be prevented by minimizing your dog's sun exposure. Internal hemangiosarcoma is more difficult to prevent. Dogs with a history of hemangiosarcoma should not be used for breeding purposes. However, many dogs are bred earlier in life, before they develop hemangiosarcoma.

Since most forms of hemangiosarcoma cannot be prevented, early detection is the next best option. The sooner cancer is detected in a dog, the better the chances of successful treatment. This is why it's so important to follow your vet's recommendation for annual or biannual wellness exams and routine screening laboratory tests.