Haemangiosarcoma in dogs: blood-vessel cancer

Overview

Haemangiosarcoma is named for its origin associated with endothelial cells lining blood vessels. It does not mean every bloody lump or every spleen tumour. A benign haemangioma is a different diagnosis. Haemangiosarcoma is estimated to account for about 2% of canine cancers. It may account for up to 50% of splenic cancers. The latter figure concerns cancers rather than all benign and malignant splenic findings.

The spleen is the most common site. In the heart, the tumour is often associated with the right atrium or atrial appendage. In skin, it may remain superficial or extend beneath the skin and into muscle. Location and depth affect behaviour. Diagnosis therefore also establishes the precise site and extent of spread.

Blood-vessel sarcomas of skin and soft tissue are often found on the trunk, hip region, thigh or extremities. Superficial sun-induced disease may remain controlled for years even if new small lesions appear.

Causes

The precise cause of most haemangiosarcomas is unknown. Inherited factors are suspected to affect susceptibility. Tumours can arise throughout the body because blood vessels are everywhere. They contain blood and may rupture readily.

Some skin haemangiosarcomas are associated with prolonged ultraviolet sunlight exposure. The same association does not apply to internal-organ disease. Unpigmented, sparsely haired skin is vulnerable to sun damage. Several separate vascular tumours may develop in a sun-damaged area.

Blood leaking from a heart tumour can collect in the sac around the heart. Fluid pressure may stop the heart filling normally. This dangerous condition is called cardiac tamponade. Abdominal bleeding and bleeding into the heart sac can therefore impair circulation through different mechanisms.

Risk factors

Internal-organ disease is seen particularly in older, large dogs. Susceptible breeds include German Shepherd Dogs, Golden Retrievers and Labrador Retrievers. Rarely, young dogs can also be affected. Breed or age nevertheless does not confirm an individual lump's diagnosis.

Breeds susceptible to sun-induced skin disease include Whippets, Italian Greyhounds and white Boxers. A thin coat and little skin pigment allow greater sun exposure. Skin and soft tissue vascular sarcomas are diagnosed most often in adult or older dogs. Sun protection needs are assessed from your dog's own coat and exposure.

Susceptibility to skin and soft tissue vascular sarcomas has also been described in Irish Wolfhounds.

Typical symptoms

There may be no signs initially. Internal-organ lesions may also be found incidentally during examination or ultrasound. At home, you may notice:

• Tiredness or general weakness.
• Reduced exercise tolerance.
• Decreased appetite.
• Pale gums or sudden collapse.
• A bruise-like skin change or blood-filled blister.
• Swelling beneath the skin without visible external bleeding.

Signs can fluctuate over time. A skin tumour may bleed externally. Fluid around the heart may be associated with fluid accumulation in the abdomen.

Skin lesions can be one or several red nodules. Sometimes a change resembles an ill-defined bruise. Growth can be rapid. Tissue death may develop within a tumour. Pericardial fluid can also be associated with coughing or vomiting.

Complications and consequences

Haemangiosarcoma can spread rapidly. Common targets include the lungs and liver. Small metastases may remain invisible on routine imaging. Rupture can cause sudden death.

For splenic haemangiosarcoma, average survival after surgery without chemotherapy is about 2 months. After surgery and chemotherapy, median survival is about 4–6 months. Fewer than 10% are alive a year after diagnosis. These figures are not used for a skin tumour confined to the surface.

Median survival after surgery for a tumour of the right atrial appendage is below 4 months. Adding chemotherapy has been associated with a reported median of 5.8 months. In contrast, superficial sun-induced skin disease can sometimes be cured surgically. A skin form extending into muscle may behave as aggressively as internal-organ disease.

The severity of pericardial signs also depends on how quickly fluid collects. With slow accumulation, the sac can stretch, so signs appear only with a large volume. Local blood clots may also form in a tumour.

Diagnosis at the vet

The vet first assesses general condition, bleeding and circulation. Investigation uses medical history and clinical examination. A blood count helps assess the patient. Blood biochemistry and clotting tests are often included too. Abdominal ultrasound and chest X-rays help assess spread.

CT is used when needed. Heart ultrasound may reveal a right atrial tumour. Ordinary X-rays do not always show it. Ultrasound is the most accurate investigation for detecting fluid in the heart sac. An ECG can be almost normal despite fluid accumulation.

The abdomen is also examined when a heart tumour is suspected. Concurrent splenic masses have been described in about 29% of dogs with suspected primary cardiac haemangiosarcoma. However, a visible heart mass is not yet a tissue-confirmed diagnosis. Pericardial fluid has other causes too, such as idiopathic inflammation.

The final tumour type is usually confirmed by tissue examination of a biopsy. Abundant blood can limit interpretation of a fine-needle cell sample. If heart tumour tissue cannot be collected safely, diagnosis may remain a strong suspicion. In skin disease, growth depth affects treatment choice.

With pericardial fluid, routine blood count, biochemistry and urinalysis may be normal. An X-ray may show an enlarged, rounded heart silhouette. However, not every patient has this typical shape. Ultrasound can assess the pressure effects of fluid.

Besides a tumour, pericardial fluid may result from injury, infection or left atrial rupture, for example.

Fluid may also be present in the pleural cavity at the same time.

Treatment

The vet prescribes treatment and medicines. The approach depends on location and spread. A splenic tumour can be removed with the spleen. Surgery may stop bleeding and reduce the risk of another rupture. Significant blood loss may require transfusion or plasma. Intravenous fluids may also be necessary.

In cardiac tamponade, fluid is removed from the heart sac through a catheter. This is called pericardiocentesis. Medicines alone generally do not remove enough accumulated fluid. Diuretics can worsen acute tamponade by reducing circulating blood volume. This differs from many ordinary heart failure treatment situations.

Surgery for cardiac haemangiosarcoma is possible only in some cases. It may be considered particularly for a tumour confined to the right atrial appendage without metastases. Removing the heart sac can relieve pressure on the heart. It does not mean the cancer itself has gone.

Chemotherapy is used to slow metastatic progression. It may help maintain good quality of life. Blood tests and imaging monitor treatment. Medication may still be considered if surgery is impossible. Where general anaesthesia is not possible, doxorubicin-based treatment has achieved a response in about 41% of patients with cardiac disease. Median survival in that setting has been about 4 months.

Radiotherapy can be used when a tumour cannot be operated on. In cardiac disease, it may reduce the need for repeated pericardial drainage. It may also be considered for local control of an incompletely removed skin tumour. Systemic medication may be needed alongside local treatment.

Superficial skin disease is often treated surgically. Wide excision is recommended for a skin tumour larger than 0.5 cm. Small, early, multiple lesions can also be treated by freezing or laser. For sun-induced lesions, size above 1 cm or a cystic structure supports surgical removal. These are veterinary treatment decisions, rather than skin changes to handle at home.

Ultrasound may guide placement of a pericardial catheter when needed. A sample of removed fluid is collected for testing. Serious drainage complications are rare. Fluids may be given immediately before and after drainage.

New approaches under investigation include immunotherapy and treatments directed at specific tumour targets.

Prevention

No reliable method of preventing internal haemangiosarcoma is known. Special diets do not reduce its development risk. Avoiding toys or other environmental objects has no preventive benefit either. Disease therefore does not mean you chose the wrong toy or diet.

Protecting a dog susceptible to sun-induced skin disease from direct sunlight is useful. Avoiding further damage may reduce new lesions. However, new tumours may still appear in previously damaged skin. Sun protection does not prevent splenic or cardiac haemangiosarcoma.

Important for dog owners

Ask for a written summary of tumour location, known growth depth, possible metastases and whether tissue has confirmed the diagnosis. Keep blood and imaging reports available if your dog attends different practices. Put treatment and recheck appointments in your calendar. Monitor appetite, breathing, exercise tolerance and weakness episodes. A dated photograph beside a measuring scale can document a skin lesion without squeezing or damaging it.

Discuss the aim of treatment: complete removal, or slowing progression and relieving signs. Agree what to do if your dog worsens at night too. Pale gums, collapse and breathing difficulty may indicate severe bleeding. Do not wait for the next recheck if these appear. During treatment, assess your dog's enjoyment of ordinary activities such as eating, resting and wanting to go out.

Frequently asked questions

Is the outlook for skin haemangiosarcoma the same as for the spleen?

No. A skin form confined to the surface can sometimes be treated surgically. Disease extending into muscle may instead behave as aggressively as internal disease. Precise tissue diagnosis, growth depth and investigation of spread are therefore essential to an individual treatment plan.

Can ultrasound confirm a heart tumour?

Ultrasound can show a right atrial mass and pericardial fluid. Imaging alone does not confirm tumour cell type. If tissue cannot be sampled, diagnosis may remain a strong suspicion used to plan treatment.

Why is the heart sac drained?

Accumulating fluid can prevent the heart filling and reduce blood pumping. In tamponade, a catheter removes the fluid. This relieves the pressure problem impairing filling, but the underlying tumour needs a separate treatment plan and monitoring.

Can chemotherapy help?

Chemotherapy is used to slow haemangiosarcoma spread. After splenic surgery, treatment may extend median survival to about 4–6 months. It may also support quality of life. Benefits and harms are assessed from tumour location, spread and your dog's condition.

Can diet prevent haemangiosarcoma?

There is no reliable known dietary measure to prevent internal disease. Sun protection may help prevent the skin form in a susceptible dog. This does not mean avoiding sunlight prevents a spleen or heart tumour. An existing skin lesion needs veterinary examination.