Hemangiosarcoma (a malignant tumor of the blood vessels) is one of the most common and most aggressive cancer types in dogs, often producing metastases at an early stage.
It usually appears in areas with rich blood supply, but it can develop almost anywhere in the body: spleen, liver, heart (pericardium/atrium), lungs, bone, skin, and under the skin. Since the tumor arises from the vessel walls, it is often filled with blood, which means it may rupture and cause life-threatening internal bleeding. It can occur at any age but is more common in older males and certain large breeds (e.g., boxers, setters, shepherds, retrievers).
Symptoms of hemangiosarcoma in dogs
There are often no early or specific symptoms, because the dog eats, plays, and appears normal. However, only after a rupture or internal bleeding do acute symptoms usually appear. The signs depend on the tumor’s location, and they may include: general weakness, lethargy, loss of appetite, vomiting, sudden weight loss, nosebleeds, fainting or collapse, anemia with pale mucous membranes, arrhythmia, abdominal fluid and bloating, as well as a reddish-purple lump on the skin or a firm, movable swelling under the skin.
The three most common forms and their characteristic symptoms
Splenic hemangiosarcoma
In the spleen, large and blood-filled lesions often develop, and these can easily rupture, which may then lead to abdominal bleeding. As a result, typical signs include weakness, pale gums, lethargy, reduced appetite, and an enlarged and tense abdomen.
Cardiac hemangiosarcoma
When the tumor is located in the pericardium or atrium, it impairs circulation, and bleeding often causes fluid accumulation in the pericardium, which leads to tamponade. As a result, symptoms such as collapse or fainting, lethargy, weakness, coughing, labored breathing, reduced stamina, and vomiting may occur.
Cutaneous and subcutaneous hemangiosarcoma
On the skin/under the skin it appears as a reddish-purple nodule or blister-like formation. If detected early and removed with wide margins, the overall condition often remains good. Warning signs: bleeding from the mass, bruising, later lethargy, lameness, loss of appetite.
Important: if you notice any of the above symptoms, seek veterinary care immediately! Hemangiosarcoma progresses rapidly, and early diagnosis can be lifesaving.
Diagnostics – how is a definitive diagnosis established?
- Physical exam and bloodwork: anemia, coagulation abnormalities, suspected liver/spleen changes.
- Imaging: abdominal ultrasound (spleen/liver changes, fluid), chest X-ray (lung metastasis), CT if necessary.
- Cytology/biopsy: the final diagnosis comes from histopathology (sample taken under safe conditions).
- Point-of-care ultrasound (FAST): for rapid detection of acute abdominal bleeding in emergencies.
Why is early detection crucial?
Hemangiosarcoma spreads quickly (liver, lungs, heart, brain), and often the first sign is rupture. Early ultrasound screening and blood tests are especially recommended in older, large-breed dogs, as they improve treatment options and safety (e.g., planned, stable surgery instead of emergency intervention).
Treatment of hemangiosarcoma in dogs
Main therapy: surgical removal (if possible) + chemotherapy (most often doxorubicin-based protocol). Surgery aims to reduce the risk of bleeding and tumor burden; chemotherapy helps reduce the chance of recurrence/metastasis.
-
-
- Splenic hemangiosarcoma: usually treated with splenectomy (removal of the spleen), and this is often combined with adjuvant chemotherapy to reduce the risk of recurrence.
- Cardiac hemangiosarcoma: often managed with pericardiectomy (opening of the pericardium) in order to relieve tamponade, while tumor removal or chemotherapy may also be considered on an individual basis.
-
- Cutaneous/subcutaneous form: surgical excision with wide safety margins; additional oncological therapy if indicated.
Palliative care: pain and bleeding management, fluid therapy, blood transfusions if needed, anti-nausea medication, gastric protection, and quality-of-life-focused care.
Role of immunomodulatory therapies in hemangiosarcoma
Immune dysregulation may also play a role in the development and progression of hemangiosarcoma. Immunomodulatory approaches aim to support the body’s own defenses and improve treatment tolerance.
- Immune cell activation: supporting T- and NK-cells to recognize abnormal cells.
- Inflammation control: reducing unfavorable tumor microenvironment inflammation.
- Regeneration support: aiding recovery after surgery/chemotherapy.
Supplements such as medicinal mushrooms (e.g., reishi, turkey tail, maitake, shiitake), omega-3 fatty acids (K9 INUKrill®) and antioxidants are currently being studied. Natural supplements aimed at supporting the immune system have shown particularly positive experiences among owners (e.g., K9 INU®, K9 INUFactor®, K9 INUExtra®, K9 Immunity™, K9 Immunity Plus™), but it is essential that you only give any supplement after veterinary consultation.
Nutrition – dietary principles for dogs with cancer
The right diet plays a crucial role in how well a dog with cancer tolerates treatment and maintains quality of life. Cancer cells primarily use sugar (glucose) for energy, so excessive carbohydrate intake may promote tumor growth. This is why a low-carbohydrate diet rich in protein and healthy fats is often recommended, supporting muscle and tissue maintenance as well as immune function.
For feeding a dog with cancer, it is advisable to provide smaller, more frequent meals, as this puts less strain on digestion and helps prevent nausea and appetite loss. Always monitor your dog’s response, and consult your veterinarian before changing the diet, since the tumor type, the dog’s age, and general condition all influence which nutrients are most needed.
For detailed guidance, read our article: feeding a dog with cancer.
Prognosis and survival times – what to expect?
Survival strongly depends on the location, extent, and presence of metastasis, as well as on the therapy that is used. The data below represent averages for guidance, but every dog’s case is individual and can differ significantly.
Survival times by type of treatment
- Surgery only (e.g., splenectomy): typically 1–3 months. Surgery may temporarily improve well-being, but the tumor often recurs or metastasizes.
- Surgery + chemotherapy: often around 4–6 months median survival. Combined therapy may delay metastasis and ensure better quality of life. Some owners report positive experiences with adding medicinal mushrooms or other natural supplements, especially in supporting the immune system.
Survival times by tumor location
- Cardiac hemangiosarcoma: typically weeks–a few months, since heart involvement rapidly leads to life-threatening complications (e.g., bleeding into the pericardium).
- Cutaneous or subcutaneous form: if detected early and excised with wide margins, prognosis is better, and many dogs may remain symptom-free longer.
Main goal: to reduce pain, prevent complications (e.g., internal bleeding), and improve and maintain quality of life. Traditional medical approaches can be complemented by natural solutions aimed at strengthening the immune system (e.g., medicinal mushrooms, omega-3 fatty acids, antioxidants).
Home care – how can you help your dog?
- Gentle lifestyle: avoid overexertion, jumping; opt for shorter, calm walks.
- Comfortable bed and easy access to water – non-slip surfaces, ramp.
- Pain management as prescribed, anti-nausea and gastric protection if needed.
- Regular check-ups: suture removal, blood tests, following the chemotherapy protocol.
- Diet and supplements: only after veterinary consultation, introduced gradually.
Prevention and screening – what can owners do?
- Annual (biannual in older dogs) internal medicine check-ups: physical exam + bloodwork/biochemistry.
- Abdominal ultrasound for higher-risk breeds/older dogs.
- Lifestyle and weight management: balanced diet, exercise, stress reduction.
Hemangiosarcoma often raises many questions for owners, such as whether it can be prevented, how painful it is, or what treatment options are available. Therefore, below we have collected the most common FAQs and answers, so that you can navigate the topic more easily and with greater confidence.
Frequently asked questions about hemangiosarcoma in dogs
❓ Can hemangiosarcoma be prevented?
Not with certainty, but annual/biannual screenings, a healthy lifestyle, and timely detection of abnormalities can improve outcomes.
❓ Is the disease painful?
It can be painful, especially in cases of rupture, internal bleeding, or tense skin/subcutaneous masses. With a modern pain plan, you can do a lot to improve comfort.
❓ How fast does it spread?
Hemangiosarcoma can spread rapidly, and the most common metastatic sites include the liver, lungs, and heart. Therefore, quick diagnosis and timely treatment are crucial, because they can significantly improve the outlook.
❓ When is chemotherapy recommended?
Often recommended as an adjunct to surgery to reduce the risk of recurrence/metastasis – your oncologist will design the treatment plan.
❓ How long can a dog live with hemangiosarcoma?
Survival depends on many factors: tumor location, extent, metastasis, treatment type. On average, it is measured in months, but in some cases modern therapy can provide over a year.
❓ Should I seek a second opinion?
Yes, especially before major decisions (e.g., surgery, chemotherapy). A second oncologist’s opinion can help you see options more clearly.
❓ What complementary therapies can help?
Immune system support, special dietary supplements, and medicinal mushrooms can be helpful – but always under veterinary supervision.
❓ Are there early signs to watch for?
Yes. For example, fatigue, pale mucous membranes, loss of appetite, abdominal mass, or sudden collapse. In such cases, see a vet immediately.
More about dog cancers
For more information, read our article on feeding dogs with cancer, check out the typical symptoms of different tumors, or browse our immune-boosting products. If you would like to read about the topic in Hungarian, click here for our hemangiosarcoma kutyáknál article, browse our other tumor-related topics, or stay up to date on why it is so important to boost your dog’s immune system.
Sources
- Clifford, C. A., Mackin, A. J., & Henry, C. J. (2000). Treatment of canine hemangiosarcoma: 2000 and beyond. Journal of Veterinary Internal Medicine, 14(5), 479–485.
- Kim, J. H., Graef, A. J., Dickerson, E. B., & Modiano, J. F. (2015). Pathobiology of hemangiosarcoma in dogs: Research advances and future perspectives. Veterinary Sciences, 2(4), 388–405.
- Chan, D. L. (2020). Nutritional support of the critically ill small animal patient. Veterinary Clinics of North America: Small Animal Practice, 50(6), 1261–1276.
- Tamborini, A., et al. (2020). Clinical outcome and prognostic factors in dogs with splenic hemangiosarcoma treated with splenectomy and adjuvant chemotherapy. Veterinary and Comparative Oncology, 18(4), 522–531.
- Wong, K., et al. (2022). Genomic landscapes of canine splenic hemangiosarcoma. PLOS ONE, 17(3), e0264986.
- Hammer, A. S., Weisse, C., & Clifford, C. A. (2021). Hemangiosarcoma. In S. J. Ettinger, E. C. Feldman, & E. Côté (Eds.), Textbook of Veterinary Internal Medicine (9th ed., pp. 2222–2232). Elsevier. ISBN 9780323672852
- Wilson-Robles, H., Miller, T., Jarvis, J., Terrell, J., Kelly, T. K., Bygott, T., … & Bougoussa, M. (2021). Characterizing circulating nucleosomes in the plasma of dogs with hemangiosarcoma. BMC Veterinary Research, 17(1), 231.
- Rodrigues, L., Watson, J., Feng, Y., et al. (2023). Shared hotspot mutations in oncogenes position dogs as an unparalleled comparative model for precision therapeutics. Scientific Reports, 13, Article number 37505.
