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Hemangiosarcoma in Dogs

Hemangiosarcoma is a type of cancer that arises from blood vessels. Hemangiosarcomas can develop on the skin, under the skin in the subcutaneous tissue, and on internal organs such as the spleen and heart. These are rare tumors in cats, but common in dogs. Continue reading to learn more about this type of cancer, diagnosis, and treatment options.

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Hemangioma versus Hemangiosarcoma

Both of these tumor types arise from the same cell lines, the vascular endothelium. Hemangiomas are benign, meaning they don’t spread to other areas. Hemangiosarcoma is an aggressive tumor that can spread to other organs and locations in the body.

Sun exposure increases the risk for both types of tumor formation on the skin and subcutaneous tissue. The tumors often appear like red to purple blisters or bumps on the skin and are typically found in areas of the body with the least amount of fur, such as the belly, scrotum, prepuce and lower limbs for dogs and the ears and face for cats. Tumors below the skin, often bleed or bruise easily, may be painful to the touch, and may cause your pet to feel ill. You might notice general symptoms such as a reduced appetite, lethargy, lameness, and pain. Both tumor types appear the same to the naked eye, so additional testing is necessary to determine what type of tumor is present.

Hemangiosarcomas on the internal organs, like the heart and spleen, aren’t influenced by sun exposure. These tumors are more prevalent in middle age to senior large breed dogs. Commonly affected breeds include Labs, Golden Retrievers, and German Shepherds. These tumors can intermittently bleed, causing panting, weakness, lethargy, collapse, pale gums, abnormal heart rate or rhythm, muffled heart sounds, and reduced appetite.

How do I know if my dog has a hemangiosarcoma?

Since both the benign and malignant forms appear the same, a biopsy is typically needed to make the diagnosis. Fine needle aspiration (FNA) and cytology rarely give a diagnosis because these types of tumors shed few cancerous cells. Unfortunately, most of the cells collected with these tests are just red blood cells.

Under sedation or general anesthesia, your vet will remove all or part of the growth(s). The tissue will be submitted to a laboratory for histopathologic testing and results are typically available within 1 to 2 weeks.

The test confirmed that my dog has hemangiosarcoma. What do I do now?

If the pathologist confirms hemangiosarcoma, they can also help determine if the tumor was completely removed or if any cancerous tissue was left behind. Most hemangiosarcomas on the skin aren’t very aggressive and surgical removal is curative. However, since most dogs and cats develop these tumors from sunbathing, they may develop additional tumors every 6 to 12 months unless you can prevent them from spending a lot of time in the sun. Over 75% of affected dogs will develop additional hemangiosarcomas in the same area.

Hemangiosarcomas of the subcutaneous tissue and internal organs are more aggressive and many have spread by the time they’ve been found. Surgical removal will help reduce the risk of severe bleeding of the tumors. Chest radiographs (x-rays) and an ultrasound of the heart and abdomen are needed to look for additional tumors/signs of metastasis.

Dogs with hemangiosarcoma of the liver, spleen, or other internal organs often have tumor metastasis by the time the main tumor is found. Once the primary tumor has been removed, the next step is chemotherapy to help slow the spread. Survival time with surgery and chemotherapy is often just 3 to 6 months. Consultation with a veterinary oncologist is ideal and you can work together to determine the best chemotherapy plan for your furry family member.

There is also a Chinese herb that can help reduce the bleeding tendencies of these tumors. This is something to discuss with your vet, as it may be started prior to surgery or used with other treatments if surgery isn’t possible.

Finally, there are studies underway about an Autologous Vaccine for hemangiosarcoma. This type of vaccine is thought to stimulate the body to attack the cancer itself. There is debate if these vaccines will work well and they aren’t available yet in the US as of January 2021.

How can I limit my dog’s sun exposure?

Keeping your dog or cat indoors as much as possible will help limit sun exposure. When inside, try to discourage them from sunbathing in windows. Keep the blinds closed, limit access to rooms with a lot of windows and sun, etc.

There are doggy UV blocking shirts available. These can help reduce sun exposure in certain areas, but not all over.

There are also sunscreens made specifically for dogs and cats. Don’t use sunscreens made for people without checking with your vet first. There are ingredients in many sunscreens that aren’t safe for dogs and cats, especially if they lick it off.

Read more:

Hemangiosarcoma is Blood or Skin Cancer in Dogs and Cats

Have more questions about cancer or tumors in dogs?

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