# Hemangiosarcoma in Dogs: Symptoms, Stages, and Prognosis Hemangiosarcoma in dogs symptoms usually appear late, often as sudden weakness, collapse, or a distended belly from internal bleeding. This cancer grows inside blood vessels, so it can spread quietly before you notice anything wrong. Knowing what to watch for helps you act fast when minutes matter. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Hemangiosarcoma is a fast-growing cancer of blood vessels, most often found in the spleen or heart of older, large breed dogs [1]. - Many dogs show no signs until the tumor ruptures and bleeds, which can cause collapse and life-threatening internal bleeding [1][2]. - Surgery alone gives a median survival of about 1 to 3 months, and adding doxorubicin chemotherapy extends that to roughly 5 to 7 months, with about 10 percent of dogs alive at one year [3]. - There is no cure, so treatment aims to control bleeding, slow the cancer, and protect comfort and quality of life [1]. - A sudden collapse, pale gums, or a rapidly swelling belly is an emergency. Call your veterinarian or an emergency hospital right away. ## What Is Hemangiosarcoma in Dogs? Hemangiosarcoma is a highly malignant cancer that starts in the cells lining blood vessels [1]. Because blood vessels run everywhere in the body, this tumor can appear in many places. The spleen and the heart are the most common sites in older, large breed dogs [1]. The tumor is made of abnormal, fragile blood channels. It grows quickly, invades nearby tissue, and spreads early to other organs, most often the lungs and the liver [1]. That pattern of rapid growth and early spread is what makes the disease so hard to treat [2]. Some dogs have a tumor that stays quiet for a long time. Others arrive at the clinic already in crisis. A splenic tumor can rupture and bleed into the abdomen, which is why the first sign is sometimes a sudden collapse [2]. ## Hemangiosarcoma in Dogs Symptoms: What Owners Notice The tricky part of this disease is that early signs are often vague or missing. Many dogs seem completely normal until the tumor bleeds [1][2]. When signs do appear, they usually fall into two groups. ### Subtle, early signs - Tiring more easily on walks - Less interest in food or treats - Occasional vomiting or a soft, loose stool - A belly that looks a little rounder than usual - Pale gums or tongue These signs overlap with many mild illnesses, so owners often wait a day or two before calling. With this cancer, waiting can be risky. ### Sudden, emergency signs - Collapse or fainting - Weakness so severe your dog cannot stand - Very pale or white gums - Fast, heavy breathing - A belly that feels tight or looks swollen - Restlessness or pacing that will not settle A dog with a mediastinal tumor (in the chest) may instead show restlessness, labored breathing, or fluid around the lungs [4]. Any of these signs means internal bleeding may be happening. Go to an emergency hospital immediately. If your dog has already had a bleeding episode, our guide to [Hemangiosarcoma in Dogs: Splenic Rupture Emergency and Recovery Support](/knowledge/veterinary-medicine/dermatology-oncology/hemangiosarcoma-in-dogs-splenic-rupture-emergency-and-recovery-support) walks through what happens next. ## Causes and Risk Factors Veterinarians do not know exactly what causes hemangiosarcoma. The disease is linked to abnormal blood vessel cells that multiply out of control, and research is still working out the molecular steps behind that change [5]. What we do know is who tends to get it. Older dogs and large or giant breeds are affected most often, and the spleen and heart are the usual sites [1]. German Shepherds and Golden Retrievers are commonly mentioned breeds, though any dog can develop it. There is no proven way to prevent this cancer, and no vaccine or diet has been shown to stop it. If your dog is a large breed and past middle age, regular wellness visits give your veterinarian the best chance to notice changes early. ## How Hemangiosarcoma Is Diagnosed Diagnosis usually starts with a physical exam and a conversation about what you have seen at home. From there, your veterinarian may recommend: - Blood work, including a complete blood count and chemistry panel - Imaging such as X-rays or ultrasound to look at the spleen, heart, and abdomen - Testing fluid in the belly or chest if bleeding is suspected - A biopsy of the tumor, which is the only way to confirm the diagnosis for certain [1] Without a biopsy, a definitive diagnosis cannot be made, but hemangiosarcoma may still be strongly suspected based on imaging and the dog's history [1]. If the tumor is in a spot that can be removed surgically, the tissue sample gives a clear answer. Newer research is exploring blood-based biomarkers and even trained detection dogs that can smell hemangiosarcoma in blood samples, with reported accuracy around 70 percent in early testing [6][7]. These tools are promising but not yet standard in general practice. ## Hemangiosarcoma in Dogs Stages You may hear owners and veterinarians talk about stages, but hemangiosarcoma does not have a single, universally used staging system like some other cancers. Instead, veterinarians describe the disease by where it started, whether it has spread, and whether the dog is stable or in crisis. A practical way to think about it: | Stage | What It Means | Typical Situation | |---|---|---| | Localized | Tumor found in one organ, no visible spread | Often found by chance during another workup | | Regional spread | Cancer has reached nearby tissue or lymph nodes | Found during surgery or imaging | | Metastatic | Cancer has spread to distant organs, most often lungs or liver [1] | Confirmed on X-rays, ultrasound, or CT | | Crisis presentation | Tumor has ruptured and is bleeding | Emergency visit for collapse or a swollen belly [2] | Staging matters because it shapes treatment. A dog with a single splenic tumor and no visible spread has more options than a dog whose cancer has already reached the lungs. Your veterinarian will explain where your dog fits and what that means for the plan ahead. ## Treatment Options Treatment depends on where the tumor is, whether it has spread, and how sick your dog is right now. ### Emergency stabilization If the tumor has ruptured, the first goal is stopping the bleeding and supporting circulation. This may include intravenous fluids, blood products, and oxygen. Some dogs need surgery quickly to remove the bleeding spleen. ### Surgery Removing the spleen (splenectomy) is the most common operation for splenic hemangiosarcoma. It is mainly palliative, meaning it controls bleeding and improves comfort, but it does not cure the cancer [2]. For tumors in the heart, surgery is far more difficult and is only possible in select cases. ### Chemotherapy Doxorubicin is the chemotherapy drug most often used after surgery. In one study of dogs with visceral hemangiosarcoma, surgery alone gave a median survival of 1 to 3 months, while doxorubicin extended median survival to 5 to 7 months, with about 10 percent of dogs alive at one year [3]. Your veterinarian calculates the exact dose from your dog's weight, kidney and liver values, and overall health. Other approaches, including metronomic chemotherapy, immunotherapy, and targeted drugs, have not shown consistent benefit so far [2]. A vaccine targeting extracellular vimentin combined with doxorubicin is being studied and showed a median survival of 235 days compared with 136 days for doxorubicin alone in a small trial, but this difference was not statistically significant [3]. Ask your veterinarian whether any clinical trial fits your dog. ### Supportive care Pain control, anti-nausea medication, appetite support, and a calm routine all matter. For dogs with tumors in the brain, surgery has been reported in rare cases, with one dog living 87 days after surgery alone [8]. These are exceptional situations, not the norm. ## Recovery, Outlook, and Long-Term Management The honest answer is that hemangiosarcoma prognosis is guarded to poor. The cancer spreads early and resists conventional treatment, so survival times are usually measured in months, not years [2][6]. That does not mean nothing can be done. Many dogs feel much better after a bleeding spleen is removed. The weeks after surgery are often good ones, with your dog eating, walking, and enjoying time with you again. Long-term management focuses on quality of life. Keep a simple log of appetite, energy, breathing rate, and comfort. Share it with your veterinarian at each visit. If your dog has other senior health issues, our article on [Dog Kidney Disease: What Do the Stages Mean for Your Dog?](/knowledge/veterinary-medicine/senior-and-chronic-care/dog-kidney-disease-stages) explains how staging works for a different condition and why lab values guide treatment. When breathing becomes labored, when your dog stops eating, or when good days become rare, that is the time to talk openly with your veterinarian about comfort-focused care. ## Prevention There is no known way to prevent hemangiosarcoma. You cannot change your dog's breed or age, and no diet, supplement, or vaccine has been proven to stop this cancer. What you can do is pay attention. Know your dog's normal energy level, appetite, and gum color. Schedule wellness exams for older large breed dogs, and mention any subtle change, even if it seems minor. Early detection is one of the few levers owners have, and researchers are actively studying ways to find this cancer sooner [7]. ## Limitations and When to Contact a Veterinarian This article cannot tell you what is happening inside your own dog. Only a veterinarian who examines your dog, reviews blood work, and sees imaging can do that. Call an emergency hospital now if your dog collapses, cannot stand, has white or pale gums, breathes fast at rest, or has a belly that looks swollen and feels tight. These signs suggest internal bleeding and need care within minutes, not hours. Call your veterinarian the same day if your dog is weak but standing, has vomited several times, refuses food for more than a day, or seems uncomfortable when you touch the belly. Schedule a routine visit if you notice gradual tiredness, a picky appetite, or a belly that looks fuller over weeks. Bring notes about when each change started. If your dog has a lump or skin mass instead, our guide to [Mast Cell Tumors in Dogs: Histopathological Grading and Treatment Guide](/knowledge/veterinary-medicine/dermatology-oncology/mast-cell-tumors-in-dogs-histopathological-grading-and-treatment-guide) explains how those tumors are graded. ## Frequently Asked Questions ### How long can a dog live with hemangiosarcoma? Most dogs live months, not years. Surgery alone gives a median survival of about 1 to 3 months, and adding doxorubicin extends that to roughly 5 to 7 months [3]. A small number of dogs live longer, so ask your veterinarian what is realistic for your dog's specific case. ### Can hemangiosarcoma be cured? No, there is no cure for hemangiosarcoma [1]. Treatment aims to stop bleeding, slow the cancer, and keep your dog comfortable for as long as possible. Some dogs do well for a meaningful stretch of time after surgery and chemotherapy. ### What are the first signs of hemangiosarcoma in dogs? Often there are no early signs at all, which is why the disease is usually found late [1][2]. When signs do show up, they may include tiredness, a poor appetite, or a slightly rounder belly. The first obvious sign is sometimes a sudden collapse from bleeding. ### Does hemangiosarcoma always start in the spleen? No. The spleen and heart are the most common sites, but tumors can form in other organs, including the chest and, rarely, the brain [1][8][4]. The location changes the symptoms and the treatment options. ### Should I choose surgery for my dog? That decision depends on where the tumor is, whether it has spread, and your dog's overall health. Splenectomy is mainly palliative and controls bleeding instead of removing the cancer [2]. Talk through the risks, costs, and expected benefit with your veterinarian before deciding. ## Related Articles - [Hemangiosarcoma in Dogs: Splenic Rupture Emergency and Recovery Support](/knowledge/veterinary-medicine/dermatology-oncology/hemangiosarcoma-in-dogs-splenic-rupture-emergency-and-recovery-support) - [osteosarcoma in dogs](/knowledge/veterinary-medicine/clinical-methods/osteosarcoma-in-dogs) - [Dog Kidney Disease: What Do the Stages Mean for Your Dog?](/knowledge/veterinary-medicine/senior-and-chronic-care/dog-kidney-disease-stages) - [Mast Cell Tumors in Dogs: Histopathological Grading and Treatment Guide](/knowledge/veterinary-medicine/dermatology-oncology/mast-cell-tumors-in-dogs-histopathological-grading-and-treatment-guide) - [Symptoms Of Dogs With Pancreatic Cancer](/knowledge/veterinary-medicine/symptom-guides/symptoms-of-dogs-with-pancreatic-cancer) - [Osteosarcoma in Large Breeds: Bone Amputation, Chemotherapy and Prognosis](/knowledge/veterinary-medicine/dermatology-oncology/osteosarcoma-in-large-breeds-bone-amputation-chemotherapy-and-prognosis) ## References 1. [Hemangiosarcoma in dogs](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/hemangiosarcoma-dogs). Cornell University College of Veterinary Medicine. 2. [Canine Splenic Hemangiosarcoma: Biological Behavior, Clinical Challenges and Therapeutic Limitations](https://pubmed.ncbi.nlm.nih.gov/41828985/). Animals : an open access journal from MDPI, 2026. 3. [Vaccination Against Extracellular Vimentin Plus Doxorubicin for Canine Hemangiosarcoma](https://pubmed.ncbi.nlm.nih.gov/41009669/). International journal of molecular sciences, 2025. 4. [Clinical features and imaging findings for a mediastinal hemangiosarcoma in a dog](https://pubmed.ncbi.nlm.nih.gov/41586149/). The Canadian veterinary journal = La revue veterinaire canadienne, 2026. 5. [Modeling Canine Hemangiosarcoma Progression Using Patient-Derived 2.5D Organoids and Orthotopic Xenografts](https://pubmed.ncbi.nlm.nih.gov/42797915/). Veterinary sciences, 2026. 6. [Hemangiosarcoma: A Systematic Review of Biomarkers in Diagnosis, Prognosis, and Therapeutic Strategies](https://pubmed.ncbi.nlm.nih.gov/41793295/). Veterinary and comparative oncology, 2026. 7. [Trained dogs can detect the odor of hemangiosarcoma in canine blood samples](https://pubmed.ncbi.nlm.nih.gov/41319895/). Veterinary journal (London, England : 1997), 2026. 8. [Surgical treatment and outcome of intracranial hemangiosarcoma in two dogs: case series](https://pubmed.ncbi.nlm.nih.gov/42038052/). Frontiers in veterinary science, 2026. ## Further Reading - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)