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Heart Cancer (Hemagiosarcoma) in Dogs

Hemangisaroma of the Heart in Dogs

Hemangiosarcoma of the heart in dogs, where “hemangio” refers to blood vessels and “sarcoma” denotes an aggressive, malignant cancer originating from connective tissues, is a prevalent cardiac tumor among canines. This tumor typically emerges from the blood vessels lining the heart, either originating within the heart itself or metastasizing from elsewhere in the body. It primarily affects mid to large-sized breeds like boxers, German shepherds, and golden retrievers, typically manifesting in dogs aged six years and older.

Detection of this tumor often occurs only when complications arise. Given its origin in blood vessels, a hemangiosarcoma can remain asymptomatic until it reaches a critical size, leading to potentially life-threatening internal bleeding upon rupture. Symptoms commonly stem from the tumor’s size obstructing the heart’s normal functioning. These may include irregular heart rhythms due to blocked or slowed blood flow, accumulation of blood or fluid in the pericardial sac surrounding the heart, or abdominal swelling exerting pressure on the heart and adjacent organs. Additionally, the resultant blood loss can trigger regenerative anemia, further complicating the diagnostic process.

Symptoms and Types

The majority of symptoms associated with hemangiosarcoma in dogs are related to complications affecting the heart rather than the tumor itself. These include:

  • Difficulty breathing
  • Accumulation of fluid within the abdominal cavity, leading to visible abdominal distention
  • Accumulation of fluid within the thoracic (chest) cavity
  • Sudden loss of consciousness or fainting (syncope)
  • Inability to perform routine exercises
  • Trouble with coordination (ataxia)
  • Irregular heartbeats or arrhythmia
  • Enlargement of the liver
  • Lethargy
  • Malaise or depression
  • Loss of appetite (anorexia)
  • Weight loss


The precise cause of hemangiosarcoma in dogs remains unknown.


Providing your veterinarian with a detailed history of your dog’s health, onset of symptoms, and any recent incidents of illness, behavioral changes, or accidents is crucial. This information can offer valuable insights into which organs are primarily affected and which are affected secondarily. Factors such as your dog’s age, breed, and outward symptoms will guide the initial diagnosis.

Standard laboratory tests, including a complete blood count, biochemistry profile, and urinalysis, are typically conducted. These tests may indicate anemia, as blood loss often leads to regenerative anemia, where the body lacks sufficient red blood cells but can still produce more to meet demand.

Fluid samples are obtained from the abdomen and chest through abdominocentesis and pericardiocentesis, respectively, for cytological analysis. This procedure not only helps in diagnosis but also provides relief by removing excess fluid. Presence of blood in the fluid sample is a common sign of hemangiosarcoma, and impaired blood clotting upon withdrawal is indicative of the body’s effort to maintain blood balance.

An electrocardiogram (ECG or EKG) is used to assess the heart’s electrical activity and may reveal abnormalities in cardiac conduction. Surgical tissue sampling (biopsy) of the mass may also be necessary for examination.

Visual diagnostic techniques such as x-rays and ultrasound of the chest and abdominal cavities can detect variations in cardiac size and structure. Echocardiography is particularly valuable for an accurate diagnosis, confirming the presence of fluid, structural abnormalities, tumor masses, or clots within the heart.


Managing hemangiosarcoma in dogs poses significant challenges as it tends to metastasize rapidly to various parts of the body. Treatment strategies aim to address both the primary tumor and any associated complications. Chemotherapy is often recommended to slow the spread of metastasis, although it cannot halt disease progression entirely. Due to the delicate location of the sarcoma, surgery may not be feasible or practical in many cases. However, if the tumor is localized to a single mass on the heart, surgery might be considered as a potential treatment option.

Your veterinarian may perform procedures to drain accumulated fluid from the thoracic and/or abdominal cavity, and pain relief medications will be prescribed to alleviate your dog’s discomfort. Unfortunately, the prognosis for this disease is generally poor, and even successful treatments may only extend your dog’s life by a few months.

Living and Management

The prognosis for dogs with hemangiosarcoma, particularly due to its location in the heart, is extremely poor in most cases. By the time of diagnosis, tumor metastasis to the lungs is often already present, complicating treatment options. Recurrence following surgery is common, and the life expectancy for affected animals is typically less than six months.

It’s important to monitor your dog closely for symptoms of recurrence and potential involvement of other body sites. If you observe signs such as difficulty breathing, sudden behavioral changes (indicating possible metastasis to the brain), or any other concerning symptoms, promptly contact your veterinarian.

Your veterinarian will provide a pain management plan for your dog and recommend a diet tailored for cancer patients. Adhere to your veterinarian’s instructions for managing your dog’s care at home diligently.

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