The vet says my dog has haemangiosarcoma - what does that mean?

Finding out that a loved one has cancer can be scary and overwhelming. Whether it’s a family member or a beloved pet, a cancer diagnosis can trigger a lot of questions and worries about what is next. Thanks to modern medicine and better nutrition, our dogs are living longer lives. But despite this potential lifespan, the possibility of developing cancer is present in any individual.

What is Cancer?

Our body is full of cells. Our organs, our blood, and all that connects the body together, is a highly complex conglomerate of different cells doing different jobs. While some cells live their life rooted in the spot as part of a fixed piece of anatomy, others such as the red and white blood cells, migrate around the body.

All cells within the body become weak or damaged over time, resulting in new cells maturing to take over from the older cells which die off and break down. This cell replenishment is a constant cycle in motion, with different types of cells having differing lifespans. Cell damage occurs either naturally through the limitation of its own function, or they can be damaged by exposure to toxins, trauma, radiation, or other adverse events.

Every now and again, a cell can mutate or doesn’t form as it should. As with damaged cells, the body’s defence responses should target and remove these cells allowing healthy tissue to form in its place. But if this mechanism fails to eliminate the abnormal cell, it can replicate and multiply. In simple terms, this is how cancers form.

Benign vs Malignant Cancer

Most people are familiar with the terms benign or malignant to describe a cancer. These words imply how a cancer is behaving, or how it is likely to behave in the future. Benign cancers are typically locally-acting growths. They are often (although not exclusively) slower to grow than malignant cancers. They may form a structured nodule or mass, or they may invade into neighbouring tissue. They do not, however, metastasise (spread) to other parts of the body further away. A lot of benign cancers may have very little effect on your dog beyond a visible growth. But benign does not always mean uncomplicated, as some of them can become ulcerated or infected, and others can trigger hormone imbalances which impact your dog’s health.

Malignant cancers by comparison are a concern not just at their primary location, but they are at risk of spreading throughout the body. The expected rate of metastasis for a malignant cancer can vary wildly, with some malignant cancers spreading very slowly, and others much more aggressively. Many malignant cancers are also fast to grow in their location, and this can cause pain and wounds externally, or pain, bleeding and functional effects if internal.

Haemangiosarcomas

The terminology used in naming cancers is based on the tissue of origin and its benign or malignant behaviour. The ending -sarcoma describes a malignant cancer originating in one of the body’s connective tissues. Haemangio- relates to the vascular, or blood, system. Haemangiosarcomas are a malignant cancer which grow within blood vessels, specifically the endothelial cell which forms the lining of these blood vessels.

They can grow anywhere in the body due to the presence of blood vessels being everywhere. They occur most commonly, however, in places where there are a high concentration of blood vessels, such as the spleen, heart and liver internally, and the skin externally. Their metastatic potential is high because blood flow can take malignant cells far away from the initial site of the tumour, allowing them to infiltrate other body parts and other organs. As such, they are often considered an aggressive form of cancer.

Breed Predisposition

Although any dog could develop haemangiosarcoma, there are certain dog breeds that are much more prone. German Shepherds and Boxers are two of the more common breeds to get this type, as well as the labrador and golden retriever breeds. Other breeds of note are Beagles, Dalmatians, and Basset hounds. Dogs with thin hair coats, such as whippets, greyhounds, and Italian greyhounds, seem to have a higher occurrence rate for the cutaneous form. This may be related to UV-induced damage to the skin cells.

Symptoms of Haemangiosarcoma

How this type of cancer presents will depend on where they start. Those that grow on the skin are known as cutaneous (if they are on the surface), or subcutaneous (if they are just below the surface). They can look like a blood blister or will appear as a red or purple lump. These are usually going to be most visible in the parts of the body with less fur, such as the groin, belly, and inside of the hindlimbs. They may start as a single growth, or they may multiply giving a rash-like appearance. Due to their origin being the blood supply, knocking or damaging these growths can result in bleeding and bruising around the lump.

Visceral haemangiosarcomas grow in one of the viscera, the collective term for the organs of the body. This type can unfortunately have much more dramatic symptoms due to the potential for life-threatening internal bleeding. Milder bleeding may be evident as bruising or spotting associated with the abdomen. Slow bleeds from visceral haemangiosarcomas can lead to anaemia which plays a role in reducing your dog’s energy levels. They may show discomfort, increased breathing, or just be increasingly tired. You may notice your dog’s gums look paler than usual or their belly looks swollen.

If one of these visceral tumours ruptures, sadly the outcome can be catastrophic

A rapid loss of blood causes an individual to collapse. These are often directly fatal if sudden and severe, or indirectly fatal due to euthanasia being sought because of compromised health and welfare. Tumour rupture is also another of the ways that this cancer metastasises through the body, with adjacent organs becoming affected through seeding of cancerous cells.

Haemangiosarcomas are more prone in middle-aged and older dogs, although they are not unheard of in young individuals. If you notice a lump on your dog’s skin, it is important to seek your vet’s opinion and follow their advice if a pathologist-reviewed aspirate or biopsy is recommended. You will know your dog’s normal behaviours best, so if you ever think they look like their tummy is swollen, or they seem unwell in any way, the sooner you get a vet exam, the sooner your dog can get treatment or relief.

Initial Management of Haemangiosarcomas

External haemangiosarcomas are easier to treat, and quick intervention may allow for remission. Upon suspicion or confirmation, the lump itself will be cut out with a margin of visibly normal tissue removed at the same time in an effort to catch migrating cells before they spread elsewhere. Your vet may discuss having an ultrasound performed to look for signs of metastatic growth, either prior to committing to surgical intervention, or after surgery, if diagnosis first requires the lump’s removal. This is part of the process of staging a cancer. Blood tests can also screen for evidence of bleeding or abnormal organ function.

Visceral haemangiosarcomas are much more complex to manage. It usually takes an ultrasound, x-rays, or CT scan to raise the suspicion of an internal mass, but these imaging methods cannot confirm the type of cancer; only tissue extraction and evaluation can do this. In organs rich with blood vessels, an ultrasound-guided biopsy may risk rupture or starting/worsening internal bleeding. Surgery may be necessary to both treat and diagnose these tumours. As with the skin variant, multiple tests will likely be indicated to stage the cancer.

The spleen is the most common organ affected by haemangiosarcoma in dogs

This is also the most common type of cancer to affect the spleen. The spleen has a role in blood storage, blood production and the immune system, but a dog can live without it. If a splenic growth is identified that has yet to spread, removal of all (complete splenectomy), or half (partial splenectomy) would be advocated. The liver, another prone site, is made up of multiple lobes. If the tumour is single and on one lobe, it may be possible to remove just the affected lobe and preserve liver function.

Organs that are less able to be operated on are the heart (the second most common site after the spleen), lungs and kidneys. Surgery in these regions require specialist intervention as the risks associated with operating in these locations are much higher. The risks may also outweigh any benefit, meaning haemangiosarcoma may be suspected in these locations but is unable to be confirmed.

Where there is evidence of metastatic spread, e.g. multiple sites or multiple organs, surgery would be purely palliative to lower the risk of immediate bleeding or may be too risky to perform at all. With advanced disease, or catastrophic rupture, your vet will discuss euthanasia, the humane ending of life. When your pet’s welfare is severely compromised, or at high risk of becoming suddenly severely compromised, euthanasia, while always a difficult and emotive decision, is a valid and often necessary means to end suffering.

Cancer Therapies

Chemotherapy and radiotherapy may be treatment options available to your dog. These can be a stand-alone treatment if surgery is not possible, or they may be an adjunct to surgery. The specific length and type of treatment will depend on the individuality of the patient’s cancer. Radiotherapy is more likely to be used after removal of a skin growth, whereas chemotherapy is more likely to be used with visceral growths. These can require regular visits to your vet clinic for treatment or may require a referral to a regional veterinary hospital or veterinary oncologist.

It is important to consider that the side-effects of chemotherapy in dogs is often not as extreme as it is in people

That being said, there are side effects and risks to weigh up. Many chemotherapy drugs require trained personnel to administer them safely, and they are often given intravenously, meaning they are not usually treatments that can be given at home. Not every dog is amenable to going back and forth to the vets, and for some individuals, the handling and regular testing involved in a chemotherapy protocol can be stressful.

Both chemotherapy and radiotherapy can have large financial outputs. This may be out-of-pocket expense, or they may be covered by an insurance policy. Where a pet is deemed suitable to receive these treatments, they may improve your dog’s quality of life and may even extend their life. They are not typically curative but focus on improving your dog’s welfare. Even with these treatment regimes, survival is often months, rather than years.

Additional Therapies

Your vet may recommend treatment that is more targeted at symptom control, in addition to the above management. The need for these depends on the symptoms that your dog has. Medication is available that can reduce bleeding, and in the case of cardiac haemangiosarcoma, functional effects such as an arrhythmia, may warrant anti-arrhythmia drugs.

Blood transfusions may be necessary to give relief from the anaemia that develops following blood loss. This can provide temporary relief of anaemia-induced lethargy and breathlessness. This may only be required once, or may require repeating, depending on individual needs. Draining fluid from an affected body cavity can be done, but the value of this can be controversial, and should be discussed with your vet at the time.

Conclusion

Haemangiosarcomas are an aggressive form of cancer that affects the lining of blood vessels. With a high rate of metastasis, the prognosis can be poor with this type of tumour. Presenting as either a skin or internal mass, the treatment and outlook will be determined by the location and spread of the tumour at the time of diagnosis. Imaging is usually required to assist with staging and diagnosing these tumours, and surgery may be necessary. In addition to operating, adjunctive therapies such as chemotherapy, radiotherapy, and symptomatic relief will be discussed. Understanding what is best for your dog, requires knowledge of your dog’s behaviour, their tolerances, and the recommendations of your veterinary team.

The vet says my dog has haemangiosarcoma – what does that mean?