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Hemangiosarcoma in Dogs

What Is Hemangiosarcoma in Dogs?

Hemangiosarcoma in dogs is a highly aggressive cancer originating from blood vessels, typically manifesting in the spleen, heart, liver, or skin. Its symptoms vary depending on the affected body systems. Hemangiosarcoma tumors consist of abnormal blood vessels that are fragile, invasive, and prone to rupture, leading to hemorrhaging into body cavities like the chest or abdomen.

Primarily afflicting middle-aged to older dogs, hemangiosarcoma can also occur in puppies as young as a few months old. Certain breeds, such as German Shepherds, Golden Retrievers, Labrador Retrievers, Boxers, Pit Bulls, and those with thin hair coats like Whippets, Greyhounds, Italian Greyhounds, Beagles, English Pointers, Dalmatians, and Basset Hounds, may be predisposed to this condition.

Due to its vascular nature, hemangiosarcoma can develop anywhere in the body, with splenic, cardiac, and cutaneous/subcutaneous types being the most common. Splenic hemangiosarcoma, affecting the spleen, is the most prevalent, often found alongside liver and cardiac hemangiosarcomas. Cardiac hemangiosarcoma typically arises in the right atrium of the heart, making it the most common cardiac cancer and the second most common site for hemangiosarcomas overall.

Other areas frequently affected by hemangiosarcoma include the liver, lungs, bones, kidneys, brain, oral cavity, abdomen, and muscles.


The symptoms of hemangiosarcoma in dogs vary depending on the affected organs. One characteristic of this cancer is its tendency to cause profuse bleeding due to its composition of blood cells and vessels. These tumors are not only invasive at their primary site but also aggressively spread to other parts of the body.

The clinical signs of the three most common types of hemangiosarcoma in dogs are as follows:

  • Splenic hemangiosarcoma: This type often leads to the formation of large, blood-filled tumors within the spleen, which becomes fragile and prone to rupture. When the spleen ruptures, it releases blood into the abdomen, resulting in acute blood loss. While some dogs may show no symptoms initially, pet owners typically observe signs such as weakness, pale gums, lethargy, decreased appetite, and a distended abdomen following a ruptured splenic tumor.
  • Cardiac hemangiosarcoma: These tumors weaken the heart’s ability to pump blood effectively, leading to bleeding into the sac surrounding the heart and lungs. As cardiac hemangiosarcoma progresses, pet owners may notice symptoms like collapse, lethargy, weakness, coughing, difficulty breathing, exercise intolerance, and vomiting.
  • Cutaneous/subcutaneous hemangiosarcoma: This type presents as a bump, blister, or nodule on or beneath the skin’s surface. When detected early, dogs with these tumors are typically otherwise healthy. Symptoms associated with skin hemangiosarcoma include the presence of a red or purple mass, often in areas with sparse fur such as the abdomen or legs, bruising around the tumor, bleeding from the tumor, and signs of lethargy, lameness, loss of appetite, weakness, or other abnormalities in dogs with more advanced or aggressive tumors.


The exact causes of hemangiosarcoma in dogs remain largely unknown. However, there is evidence suggesting a genetic component, as indicated by the predisposition of certain breeds to this condition. Additionally, skin hemangiosarcoma has been associated with exposure to ultraviolet (UV) radiation, particularly in dogs with thin or light-colored coats.

In humans, certain chemicals, insecticides, toxins, and radiation exposure have been linked to the development of hemangiosarcoma. While direct studies in dogs are lacking, it is believed that these same factors may also contribute to the development of hemangiosarcoma in our canine companions.


Veterinarians often suspect hemangiosarcoma based on observed clinical signs and medical history, but diagnosis and testing procedures vary depending on the affected body systems in individual cases. All types of hemangiosarcoma require staging to determine the extent of the disease and its severity. Staging helps determine suitable treatment options and provides a prognosis and estimated survival time for affected pets.

Upon suspicion of hemangiosarcoma, veterinarians typically recommend a series of tests including blood work, chest x-rays, abdominal ultrasound, and a cardiac echocardiogram. Advanced imaging techniques like CT scans or MRIs may be utilized to assess the spread of the disease.

Splenic hemangiosarcoma is often diagnosed following an acute collapse episode or weakness due to tumor rupture. Diagnosis may occur incidentally during a physical examination revealing an enlarged spleen or during imaging procedures like x-rays or ultrasound. A definitive diagnosis requires a biopsy of the spleen, with samples evaluated by a pathologist.

Cardiac hemangiosarcoma is diagnosed through an echocardiogram, particularly if there are signs of poor heart function or collapse episodes. Biopsy for confirmation is risky due to the tumor’s location, so diagnosis often relies on suspicion based on clinical findings and imaging results.

Cutaneous/subcutaneous hemangiosarcoma is initially evaluated through a fine needle aspirate (FNA) test, where a small sample of tumor cells is collected and examined under a microscope. However, hemangiosarcoma cells may not always be easily identified in FNAs. If suspicion remains high after an inconclusive FNA, a surgical biopsy is necessary for a definitive diagnosis.


For most cases of hemangiosarcoma in dogs, surgical removal of the tumor is the preferred treatment option. However, surgery may not always be feasible if the tumor has metastasized or if it is located on organs like the heart, which cannot be surgically removed. Surgery is commonly employed for skin hemangiosarcoma and uncomplicated splenic hemangiosarcoma.

Chemotherapy and radiation therapy are often necessary adjuncts to surgery, with or without it. These treatments have been shown to significantly prolong the life expectancy of dogs diagnosed with various forms of hemangiosarcoma. Chemotherapy helps slow tumor growth, and dogs typically tolerate it well, as the chemotherapy doses administered are different from those used in humans. While neither chemotherapy nor radiation therapy can cure hemangiosarcoma in dogs, they can greatly enhance their quality of life post-diagnosis.

Additional medications or treatments may be prescribed to alleviate side effects or complications associated with hemangiosarcoma. These may include:

  • Anti-bleeding medications
  • Procedures to drain fluid from around the heart, chest, or abdomen
  • Bioactive extracts derived from mushrooms
  • Anti-arrhythmic drugs
  • Blood transfusions

Living and Management

The prognosis for hemangiosarcoma in dogs depends on factors such as the location, size, and extent of metastasis of the tumor. Hemangiosarcoma is known for its aggressive nature and high rates of metastasis, contributing to its generally poor prognosis.

Splenic hemangiosarcoma typically carries a grim outlook, especially in cases where there is no surgical intervention or only the spleen is removed without chemotherapy. Dogs in these situations usually survive for only 2 weeks to 3 months after diagnosis. However, if the dog undergoes surgical removal of the spleen followed by chemotherapy, the survival time can extend to around 9 months. Nonetheless, less than 10% of dogs with splenic hemangiosarcoma are alive one year post-diagnosis.

Cardiac hemangiosarcoma, similar to other cardiac tumors, is incurable and carries a bleak prognosis. Treatment primarily focuses on palliative care to enhance comfort and quality of life. With chemotherapy, some dogs may survive for up to 4 months, while those untreated may survive only days to 2 weeks. Fatal arrhythmias are common in these cases.

Cutaneous/subcutaneous hemangiosarcoma generally has a more favorable prognosis, though it heavily depends on the tumor size and duration. Cutaneous hemangiosarcomas, particularly those caused by UV exposure, seldom metastasize, and dogs may live for several years post-removal. Pet owners should diligently monitor UV-exposed areas and promptly address any recurring tumors.

Subcutaneous hemangiosarcoma, which penetrates deeper layers of the skin and musculature, carries a poorer prognosis, with survival times typically measured in months. Dogs receiving treatment via surgery, chemotherapy, or radiation therapy require regular follow-up examinations, bloodwork, and diagnostic imaging to monitor disease progression.

Hemangiosarcoma in Dogs FAQs

Can hemangiosarcoma in dogs be prevented?

Regrettably, neither pet parents nor veterinarians can prevent hemangiosarcoma in dogs. Early diagnosis is paramount for improving survival rates. Regular veterinary check-ups, ideally every six months, and diagnostic tests are crucial for early detection.

Is hemangiosarcoma in dogs painful?

Hemangiosarcoma can cause pain, particularly when it leads to acute blood loss or breathing difficulties.

What are the end stages of hemangiosarcoma in dogs?

In most cases, hemangiosarcoma spreads to other organs, exacerbating the disease. These tumors, which are highly vascular and prone to rupture, progressively invade the chest or abdominal cavity as the disease advances.

How aggressive is hemangiosarcoma in dogs?

Hemangiosarcoma exhibits high levels of aggressiveness and local invasiveness, with a propensity for rapid spread to distant locations.

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