Cancer is characterized by the uncontrolled replication of abnormal cells. It can affect almost any part of your body, including your blood vessels. Although cancer is often thought of as a human disease, it also affects pets and many wild animals.

It’s estimated that more than 1.66 million humans and 4.2 million dogs are diagnosed with cancer each year in the United States. While blood vessel cancer is also common in cats, it’s not as common in cats as it is in dogs.

Cancer that forms in the lining of blood vessels is very rare in people. In humans, this cancer is called angiosarcoma. In dogs and cats, it’s called hemangiosarcoma.

In this article, we take a deeper look at blood vessel cancer in humans, dogs, and cats.

Angiosarcoma is a very rare and aggressive cancer. It makes up about 1% to 2% of soft-tissue sarcomas in humans. Sarcomas make up less than 1% of all cancers.

Angiosarcoma can occur in any part of your body, but it most commonly develops in the skin of your scalp, face, and neck.

It also commonly develops on a person’s chest wall after they receive radiation therapy for breast cancer.

Symptoms, treatment, and outlook

Here’s a look at the typical symptoms, and the treatment and outlook for someone with angiosarcoma.

  • Symptoms: When an angiosarcoma forms in blood vessels in your skin, it often causes purple-ish bruises that bleed easily and don’t heal. If an angiosarcoma grows on an internal organ, it may not cause problems until it grows large.
  • Treatment: Treatment usually consists of some combination of surgery, radiation therapy, and chemotherapy. It may also include targeted therapy or immunotherapy.
  • Outlook: Your outlook depends on factors such as how far the cancer has spread and where it’s found. About half of people live less than 16 months.

Hemangiosarcoma makes up as many as 7% of cancers in dogs. It can develop in the blood vessels of their skin or internal organs. In dogs, it most commonly develops in the spleen, right atrium/auricle of the heart, or liver.

Symptoms, treatment, and outlook

Here’s a look at the typical symptoms, treatment, and outlook for dogs.

  • Symptoms: Even dogs with large blood vessel cancers might not show obvious symptoms. Damage to the blood vessel can cause blood loss that leads to lethargy and weakness. This may be brief and appear as episodes of lethargy and weakness, rather than a gradual worsening of symptoms.
  • Treatment: The majority of hemangiosarcomas in dogs form in their spleen. Removal of the spleen with chemotherapy is the most common treatment.
  • Outlook: Hemangiosarcoma tends to be very aggressive in dogs, and they typically have a poor outlook. About half of dogs live less than 4 to 6 months.

Blood vessel cancer is rarer in cats than in dogs. It’s thought to make up about 0.5% to 2% of feline tumors. It’s typically diagnosed in middle-aged or older cats. The average age of diagnosis is 10 years. Hemangiosarcoma in cats is typically found in the skin.

Here’s a look at symptoms, treatment, and outlook in cats.


  • If hemangiosarcoma develops in the skin: You may notice one or more red to purple nodules on your cat’s skin. These masses are typically located in areas where fur is sparse and the skin is lightly pigmented.
  • If internal organs are affected: Symptoms include vomiting, weight loss, and lethargy. Symptoms may also include:
    • pale mucous membranes
    • cardiac murmur
    • labored breathing
    • rapid heart rate
    • depressed mental state
    • hypothermia (low body temperature)


In most cases, treatment for hemangiosarcoma in cats involves a combination of surgery and some combination of chemotherapy and radiation therapy.


As with dogs, cats with hemangiosarcoma have a poor outlook since it typically spreads quickly to other body parts.

Researchers don’t know exactly what causes blood vessel cancer, but it develops when genetic mutations in the cells that line your blood vessels cause these cells to replicate out of control. Inherited and environmental factors likely play a role.

Risk factors in humans

Identified risk factors in humans include:

  • radiation therapy
  • ultraviolet (UV) light exposure
  • exposure to some chemicals such as:
    • polyvinyl chloride
    • thorium dioxide
  • some hereditary syndromes
  • chronic lymphedema, buildup of lymph fluid under your skin

Risk factors in dogs

In dogs, some breeds are at a higher risk. At-risk breeds include:

  • golden retrievers
  • boxers
  • German shepherds
  • Labrador retrievers
  • schnauzers

Male dogs seem to be at a higher risk than female dogs.

Risk factors in cats

Fur helps block UV light from the sun, so cats and dogs that have sparse hair coverage might be at increased risk of developing hemangiosarcoma of the skin.

There are many parallels between angiosarcoma and hemangiosarcoma. Some genes such as TP53, PIK3CA, and ATRX are frequently mutated in both humans and animals with blood vessel cancer.

Here’s a side-by-side comparison of the two conditions:

Common locationsSkin and chest wallSpleen and other internal organs in dogs, skin in cats
PrevalenceVery rareFairly common in dogs, less common in cats
TreatmentRadiation therapy, chemotherapy, surgeryRadiation therapy, chemotherapy, surgery
SymptomsPersistent bruise on the skin, symptoms related to a specific internal organSymptoms related to a specific internal organ, a raised sore that doesn’t heal, general symptoms such as lethargy and weakness
OutlookGenerally poor, with half of people living less than 16 monthsGenerally poor in cats and dogs

What other animals get cancer?

Almost any animal can develop cancer, but some creatures develop cancer more than others. For example, researchers have found that 50% to 90% of aged mice die of cancer compared with 23% of people.

Can you get blood vessel cancer from your dog or cat (is it contagious)?

Cancer isn’t contagious. You can’t get blood vessel cancer or any other type of cancer from another person or animal. Some types of cancer such as leukemia and lymphoma are associated with certain viral infections.

How is blood vessel cancer diagnosed in humans?

Imaging techniques like CT scans, MRI, or PET scans are usually needed to find the tumor and see how far it’s spread. A biopsy can confirm the diagnosis. If the tumor is in your heart, you may also need a 3-dimensional echocardiogram.

How is blood vessel cancer diagnosed in dogs and cats?

Diagnosis is usually made by removing part or all of the tumor for laboratory analysis. Blood tests and imaging such as X-rays or ultrasounds can help support the diagnosis.

Is there any way to prevent blood vessel cancer in humans, dogs, or cats?

Avoiding prolonged exposure to UV light and certain chemicals such as arsenic may help prevent blood vessel cancer. UV light exposure has also been associated with blood vessel cancer in animals.

Blood vessel cancer is rare in humans. It can also form in dogs, cats, and other animals. It makes up a larger percentage of cancers in dogs than in humans.

Treatment for blood vessel cancer in humans and animals often includes some combination of surgery, radiation therapy, and chemotherapy. It tends to be aggressive, and those affected tend to have a poor outlook. However, researchers are continuing to examine new treatment options.