Hemangiosarcoma in Dogs: Signs, Treatment and Life Expectancy

What Is Hemangiosarcoma?

Hemangiosarcoma is a malignant tumor of blood vessel cells. It spreads early through the bloodstream, so by the time it is found it has often already spread, even if this can't be seen on scans.^3,1 More than 50,000 dogs are diagnosed in the US each year.³

Forms of hemangiosarcoma

• Splenic: the most common form; a mass on the spleen that can rupture and bleed into the belly.^12,1
• Cardiac: often on the right side of the heart (right atrium); bleeding into the sac around the heart can cause collapse.^2,3,12
• Liver and other organs.¹
• Skin and under-skin (dermal and subcutaneous): a dark red or purple lump.⁶ Forms limited to the skin are linked to sun exposure in dogs with pale skin and thin hair, and have the best outlook.^5,2,6

Signs of Hemangiosarcoma in Dogs

• Sudden weakness or collapse, sometimes followed by a return to normal energy^1,7
• Pale gums¹
• A swollen belly^4,6
• Fast or difficult breathing¹
• Episodes of lethargy or poor appetite¹
• A dark red or purple lump on the skin (skin form)^6,5
• Sometimes sudden death with no warning¹

Which Dogs Get Hemangiosarcoma?

It is most common in middle-aged and older dogs, typically 8 to 10 years old, and in large breeds. German Shepherds, Golden Retrievers and Labrador Retrievers are at highest risk.^4,1 Other breeds reported at higher risk include Portuguese Water Dogs, Bernese Mountain Dogs, Flat-Coated Retrievers, Boxers and Poodles.^3,4 Breeds predisposed to the skin form include German Shepherds, Boxers, Whippets and Pit Bull Terriers.⁵ In a study of Golden Retrievers, hemangiosarcoma was diagnosed in about 8% of females spayed after 12 months, four times the rate in intact females.¹³

Diagnosis

Hemangiosarcoma is often first found as a mass on an abdominal ultrasound, sometimes in an emergency when a dog has collapsed from internal bleeding.^4,14 An ultrasound of the heart (echocardiogram) finds a heart tumor 65% to 90% of the time, and chest X-rays look for spread to the lungs.³ A definite diagnosis usually needs the tumor itself to be examined by a pathologist after surgery; needle samples often can't confirm it and can cause bleeding, so they are usually avoided for splenic masses.^4,12,2,6 Blood tests may show anemia, low platelets or clotting changes,^12,2 but no blood test can reliably confirm or screen for hemangiosarcoma.^3,6

Not every splenic mass is cancer

You may hear of the "double two-thirds rule": that about two-thirds of splenic masses are malignant, and two-thirds of those are hemangiosarcoma. Newer research shows it depends on the situation. When a splenic mass has bled, the chance of cancer is higher than the rule suggests.^9,15 When a mass is found by chance and hasn't bled, most are benign.¹⁰ Hemangiosarcoma is also more likely in bigger dogs.¹⁶ Removing the spleen allows a diagnosis, and benign masses are often cured by surgery.^10,4

Treatment

• Emergency stabilization: fluids and blood transfusions for dogs that are bleeding.^15,14
• Surgery: removing the spleen (splenectomy) or the tumor. In one review, 95% of dogs with internal bleeding survived to go home after splenectomy.¹⁴
• Chemotherapy: usually doxorubicin-based, given after surgery to slow spread. The benefit is modest.^2,11
• Skin tumors: surgical removal with wide margins, which often gives long-term control, though new tumors can develop in sun-damaged skin.^5,2
• Palliative care if surgery isn't chosen: comfort care and a plan with your vet for what to do if a bleed happens.¹

Life Expectancy

• Untreated internal hemangiosarcoma: most dogs live only about 1 to 2 weeks after diagnosis, though some live several months.³
• Splenectomy alone: about 1 to 3 months.^3,11,1
• Splenectomy plus chemotherapy: about 4 to 6 months on average, sometimes longer.^3,1,4 Overall, only about 10% to 15% of dogs with splenic hemangiosarcoma are alive a year after diagnosis, and up to about 20% with surgery plus chemotherapy in some studies.^1,3,12
• Heart hemangiosarcoma: median survival of about 42 to 175 days (roughly 1.5 to 6 months) in published studies.²
• Skin-only hemangiosarcoma: often more than 2 years after surgery.⁵

These are averages, and some dogs do better. Your vet or a veterinary oncologist can help you decide what is right for your dog.

Caring for Your Dog and Saying Goodbye

The tumor itself is generally not painful,³ but bleeding episodes can cause sudden weakness or collapse.^1,4 Make a plan with your vet for what to do if your dog collapses. Some families, guided by their vet, choose a planned, peaceful goodbye while their dog is still comfortable. A quality-of-life scale can help you decide when the time has come.¹⁷ See also cancer in dogs and signs of cancer in dogs.

Frequently Asked Questions

What are the first signs of hemangiosarcoma in dogs?

Often none until sudden weakness, collapse, pale gums or a swollen belly from internal bleeding.

How long can a dog live with hemangiosarcoma?

About 1 to 3 months with surgery alone, and about 4 to 6 months with surgery and chemotherapy. Skin-only forms can do much better.

Is hemangiosarcoma painful for dogs?

The tumor itself is generally not painful, but bleeding episodes can cause sudden weakness or collapse, so comfort care and a plan with your vet are important.

What is the double two-thirds rule?

An old rule that two-thirds of splenic masses are cancer and two-thirds of those are hemangiosarcoma. It's now known to depend on whether the mass has bled.

Which dog breeds get hemangiosarcoma?

German Shepherds, Golden Retrievers and Labrador Retrievers most often, plus other large breeds.

Can a dog survive hemangiosarcoma?

Dogs with skin-only tumors often do. For internal hemangiosarcoma, long-term survival is uncommon.

When should I euthanize a dog with hemangiosarcoma?

When bleeding episodes, weakness or poor appetite mean bad days outnumber good ones. Your vet can help you decide.