Hemangiosarcoma is a highly aggressive and often fatal cancer that arises from the endothelial cells lining blood vessels. It accounts for about 2% of all soft tissue sarcomas in humans but is far more common and deadly in dogs, affecting up to 7% of canine cancer cases.
This stealthy tumor grows rapidly and tends to spread silently throughout the body, frequently causing sudden internal bleeding, which can be life-threatening.
In dogs, median survival times after diagnosis are typically just a few months, highlighting the urgent need for early detection and better treatments. Despite advances in veterinary and human oncology, hemangiosarcoma remains a formidable challenge due to its aggressive nature, late diagnosis, and limited treatment options.
What Is Hemangiosarcoma?
Hemangiosarcoma is a malignant cancer that originates in the blood vessel lining. It most commonly affects the spleen, liver, heart, and skin, but it can spread to other parts of the body. Since it’s a cancer of the blood vessels, tumors can grow large and rupture suddenly, leading to internal bleeding, a medical emergency in dogs.
Large breeds like German Shepherds, Golden Retrievers, and Labrador Retrievers tend to be at a higher risk, especially as they age. While it can occur at any age, hemangiosarcoma is most often diagnosed in middle-aged to older dogs.
Type of Hemangiosarcoma in Dogs
Splenic Hemangiosarcoma
Splenic hemangiosarcoma is the most common form of this aggressive cancer in dogs. It originates in the spleen, an organ that plays a crucial role in filtering blood and supporting the immune system. These tumors often grow silently until they rupture, causing sudden and severe internal bleeding. This can lead to symptoms like weakness, collapse, pale gums, and abdominal swelling.
Because of the risk of rupture and rapid disease progression, hemangiosarcoma of the spleen is often diagnosed during emergency veterinary visits. Treatment usually involves surgical removal of the spleen combined with chemotherapy, but unfortunately, the prognosis remains guarded due to early spread of the cancer.
Cardiac Hemangiosarcoma
Cardiac hemangiosarcoma most commonly develops in the right atrium of the heart, where the tumor can interfere with normal heart function. As the tumor grows, it may cause fluid to build up around the heart, a condition known as pericardial effusion, leading to difficulty breathing, lethargy, and collapse.
This form of hemangiosarcoma is particularly dangerous because symptoms often appear suddenly, and diagnosis can be challenging until advanced stages. Despite surgery and chemotherapy options, cardiac hemangiosarcoma carries a poor prognosis for dogs due to its critical location and aggressive behavior.
Cutaneous Hemangiosarcoma
Cutaneous hemangiosarcoma arises in the skin or just beneath it and often appears as a red, dark, or purple lump or lesion. Unlike the internal forms, this type tends to be less aggressive and may be associated with chronic sun exposure, especially in dogs with light-colored or thin coats. Because it is more accessible, cutaneous hemangiosarcoma is often detected earlier and can sometimes be cured with surgical removal alone. However, if left untreated, it can grow deeper and potentially spread to other parts of the body.
Visceral Hemangiosarcoma
Visceral hemangiosarcoma refers to tumors that develop in internal organs other than the spleen and heart, such as the liver, lungs, kidneys, or muscles. These tumors are less common but are still highly malignant. The symptoms vary widely depending on the organ involved but may include pain, swelling, lethargy, or signs of internal bleeding.
Visceral hemangiosarcoma is challenging to diagnose early because symptoms are often vague or mimic other conditions. Treatment usually involves surgery and chemotherapy, but the outlook remains poor due to the tumor’s aggressive nature and tendency to spread rapidly.
What Are the Early Symptoms of Hemangiosarcoma?
Early symptoms of hemangiosarcoma can be subtle and often go unnoticed until the disease progresses. Common early signs shown by dogs with hemangiosarcoma are:
- Lethargy or weakness
- Loss of appetite
- Unexplained weight loss
- Swelling or lumps under the skin
- Pale gums
- Difficulty breathing or coughing
- Abdominal Distension or bloating
- Rapid Heart Rate (Tachycardia)
1. Lethargy or Weakness
Lethargy or weakness occurs because hemangiosarcoma often causes internal bleeding, leading to a reduction in red blood cells (anemia). With fewer red blood cells to carry oxygen throughout the body, muscles and organs don’t get enough oxygen, which results in fatigue and low energy. Additionally, the body’s immune response to the tumor can cause general malaise. This symptom is usually one of the earliest signs but is very nonspecific, making it easy to overlook.
2. Loss of Appetite
Loss of appetite can happen for several reasons. The presence of a tumor can cause discomfort or pain, which reduces the desire to eat. Also, systemic effects like inflammation and the release of certain chemicals (cytokines) by the tumor or immune system can affect the brain’s hunger signals. This decrease in food intake can further weaken the body and worsen other symptoms like weight loss.
3. Unexplained Weight Loss
Weight loss occurs as the body’s metabolism changes in response to cancer. The tumor itself consumes nutrients and energy, diverting resources from healthy tissues. Coupled with reduced appetite and increased energy expenditure due to fighting the disease, this leads to rapid and unexplained loss of body mass. Dog weight loss is often a sign that the disease is progressing.
4. Swelling or Lumps Under the Skin
Hemangiosarcoma originates from blood vessel cells, so tumors can form visible lumps or swellings under the skin. These growths are typically soft because they contain blood-filled spaces. Although they may not cause pain initially, these lumps indicate localized tumor growth and blood vessel abnormalities. Over time, the lumps can enlarge or rupture, causing bleeding and pain.
5. Pale Gums
Pale gums are a classic sign of anemia caused by internal bleeding or destruction of red blood cells. Since hemangiosarcoma tumors are fragile and prone to bleeding internally, blood loss reduces the number of circulating red blood cells. This lack of red blood cells means less oxygen reaches tissues, and the mucous membranes, such as the gums, lose their healthy pink color and appear pale or white.
6. Difficulty Breathing or Coughing
If the tumor spreads to the lungs or heart, it can impair their function and cause respiratory symptoms. Tumor growth in the lungs can reduce oxygen exchange, leading to shortness of breath or coughing. Additionally, fluid buildup caused by the tumor pressing on lung tissue or heart failure may cause labored breathing. These symptoms often indicate advanced disease.
7. Abdominal Distension or Bloating
Abdominal swelling is usually caused by internal bleeding or fluid accumulation (ascites) within the abdomen. Hemangiosarcoma commonly affects the spleen or liver, and when these tumors rupture, blood leaks into the abdominal cavity, causing distension. This buildup of fluid or blood increases abdominal size and can cause discomfort or pain.
8. Rapid Heart Rate (Tachycardia)
The heart beats faster to compensate for the reduced oxygen-carrying capacity caused by anemia and blood loss. Tachycardia helps maintain blood pressure and oxygen delivery to vital organs despite the decreased number of red blood cells. This increased heart rate is an early compensatory response but can become harmful if sustained for long periods.
Do dogs feel pain with hemangiosarcoma?
Yes, dogs can experience discomfort from hemangiosarcoma, though it may not be noticeable at first. In the early stages, the tumour may develop quietly without causing much discomfort, particularly if it is deep inside organs such as the spleen or heart.
However, as the tumour grows, ruptures, or produces internal bleeding, dogs frequently experience severe pain or discomfort. Pain symptoms include restlessness, whining, reluctance to move, sensitivity to touch, and behavioural changes such as hiding or decreased activity.
How Quickly does Hemangiosarcoma Spread?
Hemangiosarcoma is one of the most aggressive and fast-spreading cancers, primarily because it originates from the cells lining blood vessels. This vascular origin gives the tumor direct access to the bloodstream, allowing cancer cells to travel rapidly to other parts of the body.
The tumor can grow silently and expand quickly, often doubling in size within weeks. By the time clinical signs appear, the cancer has frequently metastasized (spread) to distant organs such as the lungs, liver, spleen, or heart. This rapid and widespread dissemination makes hemangiosarcoma especially dangerous and difficult to treat. Unfortunately, the disease is often detected only at an advanced stage due to its subtle early symptoms.
Stages of Hemangiosarcoma
Like many cancers, hemangiosarcoma progresses through stages that describe the extent of tumor growth and spread. Although specific staging systems can vary, here is a general overview:
| Stage 1: Localized Tumor | Stage 2: Regional Spread | Stage 3: Metastatic Disease |
| The cancer is confined to its site of origin, such as the spleen, skin, or other localized tissues. Tumor size is small, and there is no evidence of spread to nearby lymph nodes or other organs. Treatment at this stage has the best chance of success, but early detection is rare. | The tumor has grown larger or started to invade surrounding tissues. Cancer cells may have spread to regional lymph nodes or adjacent structures. Symptoms may become more apparent, but systemic spread might still be limited. | Cancer cells have spread to distant organs via the bloodstream. Common sites include lungs, liver, and heart. The disease is widespread, and treatment options are more limited, focusing mainly on palliative care or slowing progression. |
How long can Dogs Live with Hemangiosarcoma?
Dogs diagnosed with hemangiosarcoma generally face a challenging prognosis due to the cancer’s aggressive nature. Without treatment, survival is often very short, typically just a few days to weeks, because of sudden internal bleeding or organ failure caused by tumor rupture.
With treatment, such as surgery to remove the tumor followed by chemotherapy, some dogs may live longer. On average, dogs receiving surgery plus chemotherapy survive around 4 to 6 months, though some may live up to a year or slightly longer in rare cases. Surgery alone usually extends survival to about 1 to 3 months.
Early detection, the dog’s overall health, and the tumor’s location also affect survival times. Unfortunately, despite aggressive treatment, hemangiosarcoma is often fatal due to rapid metastasis and recurrence.
Can hemangiosarcoma cause sudden death in dogs?
Yes, hemangiosarcoma can lead to abrupt death in dogs. This cancer frequently originates in organs such as the spleen, heart, and liver, where tumours are prone to burst. When a tumour unexpectedly bursts, it can cause extensive internal bleeding, resulting in fast blood loss and shock.
This internal haemorrhage can occur unexpectedly and lead to collapse or abrupt death if emergency treatment is not received right away. Because hemangiosarcoma grows silently and symptoms can be modest or nonexistent until a catastrophic event happens, many dogs appear healthy until the time of rupture. This is one of the reasons why hemangiosarcoma is regarded as a particularly hazardous and lethal cancer in dogs.
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How do Veterinarians Diagnose Hemangiosarcoma in Dogs?
Diagnosing hemangiosarcoma in dogs can be quite challenging because this cancer often develops silently without obvious early signs. Veterinarians rely on a combination of clinical evaluation, laboratory tests, and imaging techniques to identify the disease.
1. Physical Examination
The diagnostic process begins with a thorough physical exam. The vet carefully checks the dog’s body for any lumps, swellings, or masses under the skin, particularly in common sites like the limbs, abdomen, or chest. They also look for signs of anemia, such as pale or white gums, which may indicate internal bleeding. Abdominal palpation may reveal enlargement or fluid buildup, and the vet assesses the dog’s general condition, including heart rate and breathing.
2. Blood Tests
Blood work is crucial in diagnosing hemangiosarcoma. A complete blood count (CBC) can reveal anemia caused by internal bleeding, characterized by a reduced number of red blood cells. Other abnormalities like low platelet counts or changes in white blood cells can also indicate inflammation or bleeding disorders. Blood chemistry tests may assess organ function, helping to detect any liver or kidney involvement.
3. Imaging Techniques
Imaging is essential to visualize tumors and assess their size, location, and spread:
- X-rays (Radiographs): Chest and abdominal X-rays help detect tumors in organs like the lungs, spleen, or liver, as well as any metastasis (spread) to other areas.
- Ultrasound: This is often the most valuable tool for evaluating internal organs. An abdominal ultrasound can identify masses in the spleen or liver and detect fluid buildup due to internal bleeding. It also helps guide needle biopsies if needed.
- Echocardiogram: If a tumor in the heart is suspected, an ultrasound of the heart (echocardiogram) can assess the presence and size of masses affecting heart function.
4. Fine Needle Aspiration (FNA) or Biopsy
To confirm the diagnosis, the vet may collect a tissue sample from the tumor. Fine needle aspiration involves using a thin needle to extract cells for microscopic examination. While this is less invasive, it can be risky with hemangiosarcoma because the tumor’s fragile blood vessels may bleed easily. A surgical biopsy may sometimes be performed during tumor removal for a more definitive diagnosis.
5. Exploratory Surgery
In many cases, especially when the dog presents with internal bleeding or acute symptoms, veterinarians perform exploratory surgery. This allows them to directly visualize the tumor, control bleeding, and remove affected organs such as the spleen. Tissue samples collected during surgery are sent to a pathology lab for confirmation of hemangiosarcoma.
How is Canine Hemangiosarcoma Treated?
Hemangiosarcoma (HSA) in dogs is a particularly aggressive cancer that originates from the cells lining blood vessels. Because these tumors are often deeply embedded in vital organs like the spleen, heart, or liver, they can cause sudden internal bleeding and serious complications. Treating HSA requires a careful, multi-faceted approach aimed at controlling the tumor, slowing the spread of cancer cells, and improving the dog’s quality of life.
1. Surgery: The First Step in Treatment
The cornerstone of treating hemangiosarcoma is surgical removal of the tumor whenever possible. The goal of surgery is to physically remove the primary mass causing symptoms.
- Commonly affected organs: The spleen is the most frequent site, but the heart (especially the right atrium), liver, and occasionally the skin or muscle can also develop these tumors.
- What surgery involves: For example, if the tumor is in the spleen, a splenectomy (removal of the spleen) is performed. This surgery is urgent if the tumor has ruptured and caused internal bleeding, which can be life-threatening.
- Benefits: Surgery can relieve pain, stop or reduce bleeding, and improve overall wellbeing. It may also allow the dog to live longer by removing the largest tumor burden.
- Limitations: Unfortunately, because HSA tends to spread microscopically before symptoms appear, surgery alone rarely cures the disease.
2. Chemotherapy: Targeting Invisible Cancer Cells
Since hemangiosarcoma is known to metastasize early, chemotherapy is almost always recommended after surgery. Chemotherapy works by using drugs that circulate through the bloodstream to kill cancer cells that have spread but cannot be seen or removed surgically.
- Common drugs: The most effective and commonly used drug is doxorubicin, known for its ability to slow tumor growth. Other drugs sometimes used include vincristine, cyclophosphamide, and carboplatin, often in combination protocols.
- Treatment plan: Chemotherapy is usually given in a series of treatments spaced over several weeks to months, depending on the dog’s response and tolerance.
- Benefits: Studies show that dogs receiving chemotherapy after surgery typically live several months longer than those who undergo surgery alone. While it’s not a cure, it can improve survival time and quality of life.
- Side effects: Chemotherapy may cause side effects such as nausea, decreased appetite, low white blood cell counts, or fatigue, but many dogs tolerate it well with proper supportive care.
3. Supportive and Palliative Care: Focusing on Comfort
Not all dogs are candidates for surgery or chemotherapy, often due to advanced disease, poor overall health, or the owner’s preferences. In these cases, the focus shifts to supportive or palliative care, which aims to make the dog as comfortable as possible.
- Pain management: Using medications like pain relievers and anti-inflammatories to reduce discomfort.
- Controlling bleeding: Blood transfusions or medications might be used if the tumor causes significant blood loss.
- Maintaining nutrition and hydration: Ensuring the dog eats and drinks well, sometimes with appetite stimulants or fluid therapy.
- Monitoring: Frequent veterinary check-ups to assess the dog’s condition and adjust care as needed.
4. Emerging Treatments and Clinical Trials
Research continues into new treatment options for hemangiosarcoma, including targeted therapies that attack specific molecules on cancer cells and immunotherapy that aims to stimulate the dog’s immune system to fight cancer. These are mostly experimental at this stage but offer hope for future improvements in outcomes.
Prognosis Note
Even with treatment, canine hemangiosarcoma generally has a poor prognosis because it spreads rapidly and is often advanced by the time of diagnosis. Treatment typically extends survival by several months but rarely leads to a cure.
What dog breeds are prone to Canine Hemangiosarcoma?
Certain breeds are genetically predisposed to developing hemangiosarcoma, particularly large and deep-chested dogs. Breeds most commonly affected include:
- Golden Retrievers
- German Shepherds
- Labrador Retrievers
- Boxers
- Portuguese Water Dogs
- Flat-Coated Retrievers
If your dog is in one of these groups, regular wellness exams and monitoring are especially important after age 6 or 7.
What is the difference between a hemangima and a Hemangiosarcoma in dogs?
Hemangioma vs. Hemangiosarcoma in Dogs
| Feature | Hemangioma | Hemangiosarcoma |
|---|---|---|
| Nature of tumor | Benign (non-cancerous) tumor made up of blood vessel cells | Malignant (cancerous) tumor originating from blood vessel cells |
| Growth behavior | Slow-growing and usually stays localized (does not spread) | Rapid-growing and aggressive, often spreads (metastasizes) throughout the body |
| Appearance | Often appears as a small, well-defined lump under the skin or in soft tissues | Can form large, irregular masses, often deep inside organs like the spleen or heart |
| Risk to health | Usually low risk; may just cause a visible lump or slight bleeding | High risk; causes internal bleeding, organ failure, and metastasis |
| Treatment | Surgical removal is often curative | Requires surgery plus chemotherapy; prognosis is generally poor |
| Prognosis | Excellent once removed | Guarded to poor, even with treatment |
Hemangioma:
This is basically a harmless “blood vessel growth.” It’s a benign tumor, meaning it doesn’t invade surrounding tissues or spread to other parts of the body. Often, hemangiomas are just small lumps on or under the skin that might bleed occasionally but generally don’t cause serious health problems. They can sometimes be left alone unless they grow large or cause issues, but surgical removal usually cures the problem.
Hemangiosarcoma:
This is a very aggressive cancer arising from the same type of cells — the cells that line blood vessels — but unlike hemangiomas, these tumors grow quickly, invade nearby tissues, and frequently send cancer cells to other organs through the bloodstream (metastasis). This cancer often causes sudden internal bleeding and can be life-threatening very fast. It most commonly affects internal organs like the spleen, heart, and liver, making it harder to detect early.
