Hemangiosarcoma in Dogs

Lauren Jones, VMD
By Lauren Jones, VMD on Jun. 13, 2022
Man vet examining boston terrier with stethoscope in clinic.

In This Article


What Is Hemangiosarcoma in Dogs?

Hemangiosarcoma is an aggressive form of cancer that develops from blood vessels. It can occur anywhere in the body but most often affects a dog’s spleen, heart, liver, or skin.

Symptoms of hemangiosarcoma vary depending on the body systems involved. Hemangiosarcoma tumors are composed of abnormal blood and blood vessels that are fragile, invasive, and easily ruptured. When a tumor ruptures, it hemorrhages into a body cavity like the chest or abdomen, causing many of the clinical signs associated with hemangiosarcoma.

Hemangiosarcoma typically affects middle-aged to older dogs; but it has also been reported in puppies only a few months old. Some breeds may be predisposed to hemangiosarcoma, including:

Because of the vascular (lots of blood vessels) nature of hemangiosarcoma, it can cause cancer anywhere in the body. The most common types of hemangiosarcoma are:

  • Splenic: This is the most common type in dogs. This cancer invades the spleen, an abdominal organ primarily responsible for immune system function, red and white blood cell production, and storage of blood products. When a dog is diagnosed with a splenic tumor, two-thirds of those tumors are malignant or cancerous. Two-thirds of the malignant tumors will be hemangiosarcoma, making it the most common splenic tumor. It is often seen in combination with liver and cardiac hemangiosarcoma.

  • Cardiac: This cancer typically forms in the right atrium, one of the heart's chambers. It is the most common cancer affecting the heart and the second most common location of hemangiosarcomas.

  • Cutaneous/subcutaneous (skin): This cancer affects the skin (cutaneous or dermal) and under the skin (subcutaneous).

Other common areas affected by hemangiosarcoma include:

  • Liver

  • Lungs

  • Bone

  • Kidney

  • Brain

  • Oral cavity

  • Abdomen

  • Muscle

Symptoms of Hemangiosarcoma in Dogs

Clinical signs of hemangiosarcoma vary with the organs involved. A hallmark of hemangiosarcoma is the ability to bleed profusely, primarily because the tumors are made from blood cells and vessels. The tumors are invasive at the primary tissue site but also distantly aggressive, rapidly growing and spreading to other sites in the body.

Symptoms of the three most common types in dogs include:

  • Splenic hemangiosarcoma: The vascular nature of hemangiosarcoma commonly leads to large, blood-filled tumors within the spleen. The tissue is not healthy and is easily breakable. This damaged organ can rupture, spilling blood into the abdomen and causing acute blood loss. While some dogs can be asymptomatic for a while, pet parents most often notice clinical signs secondary to a ruptured splenic tumor, including:

    • Weakness
    • Pale gums

    • Lethargy

    • Decreased appetite

    • Distended abdomen

  • Cardiac hemangiosarcoma: This cancer weakens the heart, decreasing the ability to pump blood appropriately. These tumors are also brittle and unstable, causing hemorrhage into the sac around the heart and lungs. As cardiac hemangiosarcoma progresses, pet parents typically notice:

    • Collapse
    • Lethargy

    • Weakness

    • Coughing

    • Difficulty breathing

    • Exercise intolerance

    • Vomiting

  • Cutaneous/subcutaneous hemangiosarcoma: This type of hemangiosarcoma may appear as a bump, blister, or nodule in or under the skin's surface. Especially when caught early, dogs with these tumors are usually otherwise healthy. With skin hemangiosarcoma, pet parents typically note:

    • Red or purple mass, usually in areas of little fur such as the abdomen or legs
    • Bruising around the tumor

    • Bleeding from the tumor

    • Lethargy, lameness, loss of appetite, weakness, or other abnormalities in dogs with more aggressive or progressed tumors.

Causes of Hemangiosarcoma in Dogs

Most causes of hemangiosarcoma are not known. It likely has a genetic link, as shown by the predisposed breeds. Skin hemangiosarcoma has been linked to UV exposure, especially in thin, light-coated dogs.

In humans, some forms of chemicals, insecticides, toxins, and radiation have been linked to hemangiosarcoma development. While there aren’t any direct studies in dogs, these factors are also believed to cause hemangiosarcoma in our pets as well.

How Veterinarians Diagnose Hemangiosarcoma in Dogs

Veterinarians may suspect hemangiosarcoma based on clinical signs and history. Because hemangiosarcoma can affect any body system, testing and diagnosis is different based on individual cases.

All forms of hemangiosarcoma involve staging, which is a determination of the severity and spread of the disease. Staging will decide available treatment options for pets and develop a general prognosis and expected survival time.

Once a veterinarian suspects hemangiosarcoma, they will typically recommend bloodwork, chest x-rays, an abdominal ultrasound, and a cardiac echocardiogram. Advanced imaging, such as a CT scan or MRI, can help figure out the extent of disease spread.

Splenic hemangiosarcoma

Veterinarians may diagnose a dog with splenic hemangiosarcoma after an acute collapse episode or weakness after a tumor ruptures. Often, splenic hemangiosarcoma is diagnosed after a veterinarian feels an enlarged spleen or incidentally discovers a mass on the spleen during an x-ray or ultrasound. For a definitive diagnosis, the spleen must be biopsied, and the samples must be evaluated by a pathologist.

Cardiac hemangiosarcoma

Heart tumors are usually diagnosed by an ultrasound of the heart, known as an echocardiogram. Veterinarians may suspect a heart tumor after episodes of collapse and other evidence of poor heart function. These tumors may also be discovered incidentally on routine chest x-rays.

A biopsy would also be required for a definitive diagnosis, but due to the location of the tumor around the heart, a biopsy is dangerous and typically not recommended. Most cardiac tumors are suspected to be hemangiosarcoma, but few are confirmed.

Cardiac hemangiosarcoma is commonly discovered with other types of hemangiosarcoma, most notably of the spleen. During the diagnostic workup process for splenic hemangiosarcoma, veterinarians typically closely evaluate the liver, lungs, and heart, which are all common places for hemangiosarcoma to spread.

Cutaneous/subcutaneous hemangiosarcoma

Veterinarians typically start diagnosing skin tumors with a test called a fine needle aspirate (FNA). To perform an FNA, a veterinarian will use a needle to collect a small sample of tumor cells. These cells are then evaluated under a microscope.

Some tumors easily shed cells during this process; however, most FNAs performed on hemangiosarcomas are only blood-filled and do not readily offer a diagnosis. A non-diagnostic FNA may raise a veterinarian’s suspicion of cutaneous or subcutaneous hemangiosarcoma. A surgical biopsy is required for a definitive diagnosis.

Treatment of Hemangiosarcoma in Dogs

Surgical removal of the tumor is the treatment of choice for most hemangiosarcomas. However, surgery is not always a practical option for tumors that have spread or are on organs that cannot be removed, like the heart. Surgery is most often used in cases of skin hemangiosarcoma and uncomplicated splenic hemangiosarcoma.

Many forms of hemangiosarcoma will require chemotherapy and radiation therapy, with or without surgery. These treatments can greatly extend the life expectancy for most types of hemangiosarcoma. Chemotherapy slows the growth of tumors, and dogs typically handle it very well, as the doses of chemotherapy medications are different than those used in humans. Neither chemotherapy nor radiation will cure dogs of hemangiosarcoma, but they can increase their quality of life after their diagnosis.

Other medications or treatments may be used to help minimize side effects or complications of hemangiosarcoma, such as:

  • Anti-bleeding medications

  • Procedures to remove fluid from around the heart, in the chest, or in the abdomen

  • Bioactive extracts from mushrooms

  • Anti-arrhythmic drugs

  • Blood transfusions

Recovery and Management of Hemangiosarcoma in Dogs

Hemangiosarcoma prognosis depends on tumor location, size, and spread to other organs (metastasis). Hemangiosarcoma is highly aggressive and locally invasive and has elevated metastasis rates. Cases caught and treated early can mean a longer life expectancy for your pet, although hemangiosarcoma mainly carries a poor prognosis.  

Splenic hemangiosarcoma has a poor predicted outcome, especially in cases with no surgical intervention or only surgical removal of the spleen without chemotherapy. These dogs typically live between 2 weeks and 3 months after diagnosis. If the dog is a candidate for surgical removal of the spleen and chemotherapy, the survival time increases to around 9 months. However, fewer than 10% of dogs with splenic hemangiosarcoma are alive 1 year after diagnosis.

Cardiac hemangiosarcoma, like most other cardiac tumors, is incurable and comes with a grave prognosis. Treatment for these dogs is palliative care, which helps to increase comfort and quality of life. Some dogs may live up to 4 months if treated with chemotherapy, and days to 2 weeks if not treated. These dogs have a high rate of fatal arrhythmias.

Cutaneous/subcutaneous hemangiosarcoma carries a better prognosis, although it is highly dependent on tumor size and how long it has been present. Cutaneous hemangiosarcomas, especially those caused by UV, rarely metastasize, and dogs may survive for years after removal. Pet parents must be vigilant in monitoring areas exposed to UV and have any tumors that recur removed.

Subcutaneous hemangiosarcoma carries a worse prognosis, as the tumor invades the deeper layers of the skin and musculature. Survival times of these dogs may only be in months.

Dogs treated with surgery, chemotherapy, or radiation therapy require frequent follow-up exams, bloodwork, and diagnostic imaging to assess disease progression.

Hemangiosarcoma in Dogs FAQs

Can you prevent hemangiosarcoma in dogs?

Unfortunately, there is nothing pet parents or veterinarians can do to prevent hemangiosarcoma in dogs. Early diagnosis is crucial for longer survival times. Frequent veterinary exams (at least every six months) and diagnostic testing are essential to diagnose hemangiosarcoma early.

Is hemangiosarcoma in dogs painful?

Hemangiosarcoma may be painful when it causes acute blood loss or difficulty breathing.

What are end stages of hemangiosarcoma in dogs?

Most types of hemangiosarcoma spread to other organs in the body, causing further disease. These tumors are highly vascular (blood vessel-related) and will rupture into the chest or abdominal cavity as the disease progresses.

How aggressive is hemangiosarcoma in dogs?

Hemangiosarcoma is highly aggressive and locally invasive, with high spread rates to distant sites.


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Featured Image: iStock.com/Ridofranz


Lauren Jones, VMD


Lauren Jones, VMD


Dr. Lauren Jones graduated from the University of Pennsylvania School of Veterinary Medicine in 2010, after receiving her bachelor's degree...

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