A Canine Killer: Hemangiosarcoma in Dogs

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By: Lezanne Winshaw Updated: April 17, 2020

dog looking sad with spleen cancer in dogsHemangiosarcoma (HSA) is a blood vessel-based cancer mostly found only in dogs. Unfortunately, as with humans, cancer is the leading cause of natural death in dogs. Nearly 50 % of dogs who live beyond the age of 10 will contract some form of cancer. Some of these are easily curable or treatable. Hemangiosarcoma in dogs, however, is a very serious diagnosis.

What is Hemangiosarcoma?

‘H(a)em’ refers to blood – ‘angio’ refers to ‘heart’ and ‘sarcoma’ refers to aggressive, malignant cancer. Canine Hemangiosarcoma is one of the most common types of metastatic disease affecting dogs.

HSA in dogs is an aggressive, malignant cancer within the blood vessels. More specifically, the endothelium surrounding the blood vessels.

The tumors are extremely metastatic (meaning they spread). They often spread to the brain, as well as the lungs, spleen, kidneys, heart, bone and skeletal muscle. This sarcoma also affects organs and tissues such as the liver, uterus, urinary tract and oral cavity.

Types of Hemangiosarcoma in Dogs

Because this cancer starts in the endothelial cells of blood vessels, it can present anywhere in the dog’s body. Yet, it is most likely to form malignant tumors in the spleen, liver or heart.

Dermal Hemangiosarcoma

Dermal, or cutaneous hemangiosarcoma, is the form of this canine cancer found in the skin. It presents as a red or black growth on the skin. Dermal HSA has the best prognosis. If the tumor is detected early, and before it spreads to other tissue types within the body, surgical removal could result in a complete cure.

The most likely cause of this form of canine hemangiosarcoma is exposure to the sun. Areas most likely affected are those with little or no fur. For example, the abdomen and noses of short haired dogs.

Hypodermal Hemangiosarcoma

This form of this malicious cancer also shows as a dark red blood mass. However, it forms beneath the skin and you often can’t see in on the surface of the skin. You can only detect it by pressing down on the skin and feeling a lump.

These tumors are not as visible as those of dermal hemangiosarcoma. Therefore, they stand an even greater chance, up to 60%, of not being detected before spreading to other tissues.

Splenic Hemangiosarcoma

This is the most common form of hemangiosarcoma, it’s a visceral HSA found in the spleen. The spleen is a large abdominal organ. It helps to fight against infections and removes dead red blood cells from the circulatory system.

Hemangiosarcoma of the spleen poses a threat due to splenic tumors breaking which results in profuse bleeding. The abdominal cavity fills up with blood, which leads to pressure on other internal organs.

It also leads to hypotension (low blood pressure) as there is less blood present in a dog’s circulatory system. This causes lethargy, dizziness, pale gums, and in extreme cases, collapse.

While a splenectomy (surgical removal of the spleen) is a treatment option, it is not always 100 % curative. That’s because this sarcoma spreads so quickly. Unfortunately, 1 in 4 dogs that have splenic HSA, also present with a cardiac HSA.

hemangiosarcoma in dogs black labrador being checked by vet

Heart-Based Hemangiosarcoma

This form of hemangiosarcoma is the most life-threatening. The metastatic tumors usually form in the blood vessels surrounding the heart. Angiosarcoma also poses a threat due to the tumor breaking and bleeding into the surrounding area.

In the case of cardiac HSA, this bleeding usually occurs within the pericardium. The pericardium is the tissue enclosing and surrounding the heart.

Once the tumor ruptures and begins to bleed, it can fill the pericardium. This places extra pressure on the dog’s heart and prevents it from pumping effectively. Known as pericardial effusion, this can result in severe health complications.

What are the Potential Causes of this Cancer in Dogs?

We don’t know much about the causes of this cancer. It is believed that the dermal form of this cancer is caused by excessive sun exposure.

The fact that certain dog breeds are predisposed to this illness also shows that there is a genetic link to the cause of the disease.

Because hemangiosarcoma rarely occurs in humans, there is very little research available on the cause.

Which Dogs are More Likely to Get this Illness?

This disease is most often reported in medium to large sized dog breeds. German Shepherds, Dobermans, Golden Retrievers, Labrador Retrievers, English Setters, and Boxers are breeds more likely to get HSA.

Dogs with short white hair are also more susceptible to dermal HSA. These include breeds such as Dalmatians, Bull Terriers, and American Pitbull Terriers.

It mostly occurs in middle-aged to older dogs, although, it has also been diagnosed in puppies younger than a year old. It is thought that male dogs are more susceptible than female dogs to contracting this cancer.

Common Signs and Symptoms to Look Out For! 

Because the tumors are most often present in internal organs, the disease is usually quite advanced before it’s detected. There is often very little warning in the early stages. It is estimated that the time from detection of the tumor until death is between 6 and 8 weeks. A dire prognosis.

Dermal hemangiosarcoma can be distinguished by the red or black growth on the hairless areas of the dog. The mass may become ulcerated and bleed.

Rupture of a splenic tumor can result in abdominal distension, anemic mucous membranes, and increased heart and respiratory rates.

Cardiac sarcoma will produce clinical signs related to the size of the tumor affecting normal heart function. For example; blocking or slowing of the blood pumping into or out of the heart will result in arrhythmia (irregular heartbeat).

The early stages of hypodermal and visceral hemangiosarcoma can yield the following symptoms:

  • Bleeding from the nose
  • Slow wound healing rate
  • Exercise intolerance
  • Increased respiratory rate
  • Abdominal swelling
  • Pale color of the gums and mucous membranes surrounding the eyes

Symptoms seen in late stages of the disease:

  • Distended abdomen
  • Breathing difficulty, panting and/or gasping for breath
  • Trouble with coordination (ataxia)
  • Irregular heartbeat (arrhythmia)
  • Black, tarry stool
  • Sudden loss of consciousness or fainting (syncope)
  • Inability to get up

x-ray of dog abdomen to test for hemangiosarcoma

A Look at the Treatment Options

Treatment of hemangiosarcoma depends on the extent of the disease. The size of the tumor, its location, and whether the cancer has spread from its primary site, will all determine the treatment plan.

Cutaneous Hemangiosarcoma Treatment

If you catch it in its early stages, you can treat it by simply removing the tumor, often in combination with a course of chemotherapy.

Visceral Sarcoma Treatment

A combination of surgery to remove the tumors, and chemotherapy, can treat this cancer. A median survival time of 1-4 months can be expected if the primary tumor is removed. The addition of chemotherapy can lengthen the median survival time to 6-8 months.

Several chemotherapy protocols are available. These may include any of the following drugs: vincristine, doxorubicin, cyclophosphamide, and Cytoxan.

Chemotherapy has numerous adverse side effects. The quality of life post-surgery, and with these kinds of medications, must be weighed up against the relatively short survival period.

A New Treatment Method?

A new method of drug administration, called metronomic chemotherapy, can reduce the negative side effects while increasing the efficacy of the treatment. This method involves lower doses of the typical chemotherapeutic drugs administered more frequently with few or no rest periods.

Side effects are much milder than with traditional chemotherapy. While this modality does not always result in complete destruction of the tumor, it can prevent it from expanding and metastasizing. The dog can thus live as with a chronic illness (such as diabetes or arthritis) and have a fairly comfortable and extended existence!

Splenic Hemangiosarcoma Treatment

A splenectomy is an option. Unfortunately, due to the prolific nature of this cancer, invasion into surrounding areas is likely. Removal of all cancerous tissue is not always possible.

Techniques that can treat or manage HSA, are radiation therapy, chemotherapy or managed hyperthermia (medically-induced elevation of the body temperature). This may help in prolonging a dog’s life, but it’s not always a cure.

surgical removal of tumors caused by liver cancer in dogs

Is There a Cure?

If the disease is diagnosed in its early stages and surgical removal of the tumor can prevent its spread to other parts of the dog’s body, the prognosis is good. If you have the tumors removed, the dog could still enjoy many happy years.

The disease is usually quite advanced by the time symptoms lead to examination or the discovery of tumor/s. Surgical removal of tumor/s can extend life. However, because this disease spreads so rapidly, the prognosis is not great.

Prevention is Better Than Cure

Dogs with light-colored fur, short hair or thin haired coats are most susceptible to dermal hemangiosarcoma. Don’t leave these dogs outside in the sun for too long! Perhaps even consider some doggie sunscreen.

Feed your dog a good quality, veterinarian-approved diet, and make sure they always have fresh drinking water. This can go a long way in ensuring a long, healthy and disease-free life.

Regular, annual check-ups and vaccination boosters are important. A thorough physical examination by your veterinarian once a year can identify clinical signs of diseases or disorders of internal organs even before you will spot symptoms of illness in your dog.

Common Questions

Which Dog Breeds Are Most Likely to Get HSA?

Is There a Cure for HSA?

What Causes Canine Cancer?

What are the Symptoms of HSA?

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