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Hemangiosarcoma in Dogs – 9 Silent Symptoms of a Medical Emergency

Hemangiosarcoma is a cancer that starts in the endothelial cells which are the cells that line the blood vessel walls. Unfortunately, it’s not entirely known what causes this cancer in dogs.

Risk factors for hemangiosarcoma may include:

  • Genetics – certain breeds may be more prone to this type of cancer.
  • Ultraviolet light exposure
  • Abnormal genes
  • The abnormal development of new blood vessels.

If your dog has recently been diagnosed with this form of cancer, you’re probably wondering what to expect.

Understanding the disease, treatment options, and median survival time are likely on the top of your list. Typically, this type of cancer is seen in older dogs.

This most covers all that and more. Keep reading to learn more about what hemangiosarcoma really is, what it means for your dog, and what to do going forward.

Tell Me More About Hemangiosarcoma in Dogs

Hemangiosarcoma is a devastating diagnosis for any pet owner.

Unfortunately, it doesn’t often produce noticeable symptoms until the cancer has already metastasized. It tends to occur in middle-aged or geriatric dogs.

Hemangiosarcoma does not cause dogs Unfortunately, there are few symptoms, and if the disease is found it has most often already metastasized.

Hemangiosarcoma is often divided into three different classifications, including the common primary sites:

Hemangiosarcoma in dogs is often deadly


This classification is related to the skin. The first visible sign is usually a red or black growth on the skin.

These masses can bleed and ulcerate. Unfortunately, about 33% of these masses will eventually spread to internal organs. Cancers that spread are called metastatic.

Dermal hemangiosarcoma has the best survival rate in dogs if it is caught, diagnosed, and removed before it has a chance to spread to internal organs.

Subcutaneous Hemangiosarcoma

This refers to the layer just beneath the skin, which is known as the subcutaneous tissue or hypodermis.

The top of the skin may look normal, but beneath it are dark red or black growths. Pet owners notice these when they discover a lump under the skin.

It’s thought that about two-thirds of these tumors spread to internal organs.

Visceral Hemangiosarcoma

Visceral hemangiosarcoma, also known as splenic hemangiosarcoma, is an aggressive cancer that affects the internal organs. Organs commonly affected include the spleen, heart, and liver.

This is life-threatening because tumors tend to rupture and hemorrhage.

“It is estimated that this cancer accounts for more than 5 – 7% of all tumors in dogs.”

Canine Hemangiosarcoma – The Road from Despair to Hope
Michelle G. Ritt, DVM, DACVIM; Tessa Breen, BSc (Hons), Dip GD, CMM

Diagnosing Hemangiosarcoma in Dogs

Pet parents should get new lumps or bumps found on their dogs checked by a veterinarian. It’s impossible to diagnose a lump just by looking at it or feeling it.

A biopsy, in addition to other tests, are required to make a definitive diagnosis.

Cell Aspiration

The veterinarian should aspirate cells from the tumor to determine the type of growth. Unfortunately, dogs may not have any obvious signs or symptoms until a tumor ruptures. When a rupture occurs, the dog will suffer from life-threatening internal bleeding.

Complete Blood Count

Blood tests measure red blood cells, white blood cells, and platelet counts. They are also used to assess liver and kidney function, measure electrolyte balance (sodium and potassium levels) and measure gastrointestinal enzymes.

Promising Research

Research conducted by the University of Minnesota has discovered a breakthrough in early diagnosis of hemangiosarcoma in dogs.

Early diagnosis could extend the life expectancy of a dog beyond what could previously be imagined.

The test is used to determine the presence of HSA in the blood. The presence of HSA in the blood does not necessarily mean the dog has cancer. However, it could indicate that the dog is at high risk.

Once HSA is detected, the aim is to prevent the disease through the use of a new drug known as eBAT. This new drug formulation is designed to target tumors while causing the least damage possible to the immune system.

This is still in clinical trials and subject to further peer review and study.

For more information, read: Breakthrough in Hemangiosarcoma Treatment in Dogs


Urinalysis is used to determine renal function in dogs.

Radiograph/Chest X-Rays

This is a non-invasive way to screen for any changes to the heart and lungs. It can also be used to determine signs of cancer spread.

Abdominal Ultrasound

This procedure takes an image of the abdomen to determine whether the organs appear normal in size and shape. It can also identify tumors in internal organs.


This is a sonographic exam of the heart to determine how well the heart is functioning. It can confirm whether there is abnormal fluid in the sac around the heart (this is known as pericardial effusion). If there is fluid, it may be caused by a bleeding tumor.

When blood fills the sac that encases the heart muscle, it results in a serious medical condition known as cardiac tamponade. This can lead to organ failure, shock, and death.

Signs of cardiac tamponade including:

  • anxiety
  • restlessness
  • low blood pressure
  • weakness
  • rapid breathing
  • fainting

What Breeds Are More Susceptible to Hemangiosarcoma?

This type of cancer tends to most commonly affect the spleen and heart (angiosarcoma) of Golden Retrievers, Labrador Retrievers, and German Shepherds.

Other breeds susceptible include Portuguese Water Dogs, Bernese Mountain Dogs, Boxers, and others.

Diagnosing a spleenic tumor requires a biopsy

The One Ray of Hope in an Otherwise Deadly Disease

Dermal hemangiosarcoma can be considered curative if found, and removed, very early before it has had time to spread. If you see or feel any type of suspicious lump on your dog it’s important to have it aspirated by a licensed veterinarian.

Lumps and bumps on a dog must be evaluated by a licensed veterinarian in order to get a clear diagnosis.

Early detection of dermal hemangiosarcoma on a dog are key to long-term survival. If not diagnosed and removed early, approximately 33% of these tumors will spread to internal organs.

Median Survival Rate (Life Expectancy) of Dogs with Hemangiosarcoma

Without surgery, the average survival time can be anywhere from days to weeks.

This can vary depending on where the mass is located. Splenic masses can rupture at any time. The result is a severe internal bleed which is fatal if not treated immediately.

Sadly, dogs diagnosed with hemangiosarcoma have a poor prognosis.

Clinical staging is an important factor in determining life expectancy.

Unfortunately, even dogs who undergo surgery to remove the tumor and chemotherapy to kill additional cancer cells, the survival rate is approximately 4 – 6 months.

Surgery alone (without chemotherapy) could bring survival rates down to as low as 1 – 2 months.

Effectively treating this type of aggressive cancer is challenging at the best of times. If discovered early, surgical removal along with chemotherapy and radiation can help to extend your dog’s life.

“Considering the lifetime risk of cancer for dogs is between 1 in 2 and 1 in 3 , we can calculate that 1.5 to 2.5 million of the 72 million pet dogs in the United States today will get hemangiosarcoma and succumb to it.”

Jaime F. Modiano, VMD, PhD, Michelle G. Ritt, DVM, DACVIM, Matthew Breen, PhD, CBiol, MIBiol and Tessa Breen, BSc (Hones), Dip GD, CMM
University of Colorado Health Sciences Center, Denver, CO (JFM), Animal Hospital Center, Highlands Ranch, CO (MGR), and North Carolina State University (MB, TB)

Hemangiosarcoma Symptoms in Dogs

The signs of hemangiosarcoma in dogs are considered to be non-specific.

Vague signs like the ones listed below could be caused by a variety of common illnesses in dogs.

Unfortunately, it’s usually not until a tumor erupts and causes a severe internal bleed that the diagnosis is made.

Signs include:

  • Loss of appetite (also known as inappetence)
  • Weight loss
  • Fatigue
  • Unable to endure normal play/exercise
  • Vomiting
  • Diarrhea
  • Pale Gums
  • Increased breath rate/panting

Canine Hemangiosarcoma Stages

The stages of hemangiosarcoma are defined by where the cancer is found.

Stage 1 Hemangiosarcoma in Dogs

Tumor is found only in the spleen.

Stage 2 Hemangiosarcoma in Dogs

The splenic tumor has ruptured and may involve the lymph nodes.

Stage 3 Hemangiosarcoma in Dogs

At stage 3, the cancer has spread to the lymph nodes and other tissues.

When to Euthanize a Dog with Hemangiosarcoma

The decision to euthanize a dog does not come easily, but it should be weighed with the dog’s quality of life. The most unfortunate thing with hemangiosarcoma is that it is often diagnosed at a late stage when it is more difficult to treat.

Dogs with hemangiosarcoma often have few observable signs. Your dog could be happy and playing one minute and then collapse in shock the next.

When considering quality of life, determine whether your dog is still able to do the things he/she did before. Consider the following:

Level of Pain

Is your dog in pain and, if so, are medications able to alleviate some of that?


Is your dog still eating or able to keep food and water down?


Can your dog walk independently and is he/she able to go outside to use the bathroom without trouble?


Is your dog too ill to sit up, stand, walk to their food dish, etc.?

A failing dog will likely be very quiet and still. You may see a diminished personality and an aversion to things he/she used to love. When you dog gets to this stage, especially if he/she is in pain, it may be time to speak to a veterinarian about euthanasia.

Hemangiosarcoma in dogs can cause internal hemorrhage

Cancer Treatments for Dogs with Hemangiosarcoma

Veterinary medicine continues to evolve, working hard to ensure long and happy lives for our pets. There are many different treatment options for hemangiosarcoma including the following:

Surgical Intervention

Surgical treatment is common in removing hemangiosarcoma tumors.

Although not all splenic masses are malignant (cancerous) there is no other way to determine that without surgical removal. Ideally, the mass found is nothing more than a benign tumor.

The goal of surgery is to remove the mass before it has a chance to rupture. An internal rupture will lead to dangerous blood loss.


The main chemotherapy drug used to treat this cancer is doxorubicin (adriamycin). Most dogs tolerate chemotherapy remarkably well with few side-effects. Side effects, however, can include:

  • stomach upset
  • decrease in appetite
  • nausea
  • vomiting
  • diarrhea
  • fatigue
  • decrease in white blood cell count
  • thinning of fur

Metronomic Chemotherapy

Metronomic chemotherapy is a new type of chemo where anti-cancer drugs are given in lower doses over a long period of time.

Traditionally, chemotherapy is administered in the highest dose possible (without causing too many severe side-effects) to rid the body of cancer cells.

The idea behind metronomic chemotherapy is to help control the spread of the disease and possibly increase lifespan.

The best thing about this type of therapy is that the drug can be given at home. The low dose is meant to help the immune system and lessen the growth of blood vessels that aid cancer growth.

Blood Transfusions

If emergency surgery is warranted, blood transfusions may be required depending on how much blood loss has occurred.

Alternative Treatment

Yunnan Baiyao is a Chinese herbal mixture used in veterinary patients with hemorrhage. This is considered a palliative treatment option that might slow bleeding.

READ: Yunnan Baiyao for Dogs – 5 Crucial Things You Should Know


Unfortunately, this is a very sad and difficult stage.

You may feel guilt and anxiety about what to do. Deciding on the best time to euthanize a dog with hemangiosarcoma is the worst decision a dog owner has to make.

By learning all you can about this type of cancer including the potential treatment options, you are giving yourself more control over the situation. Ultimately, hemangiosarcoma is a terrible diagnosis for anyone.

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