What is haemangiosarcoma?

Haemangiosarcoma is an aggressive type of cancer which arises from cells that line blood vessels. In this blog we will focus on haemangiosarcoma in dogs as, although it can occur in other species such as cats, this is very rare.

Where do dogs get these tumours?

These tumours have a point of origin (primary tumour), but very often metastasise (spread) to other organs causing tumours elsewhere (secondary tumours).

As blood vessels are almost everywhere in the body, they can occur in many places. Primary tumours most commonly appear on the spleen, but they are also frequently seen in the heart, liver, skin and subcutaneous tissue.

Haemangiosarcoma is the most common type of tumour affecting the heart, accounting for around 69% of heart tumours. It is also the most common malignant tumour to affect the spleen. Much of this blog will relate to haemangiosarcoma of the spleen (splenic), as this form often creates the most discussion, concern, and questions.

Why did my dog get this?

We do not know why certain individual dogs are affected, although we know that, in skin, haemangiosarcoma is linked to sun exposure.

Certain breeds are predisposed. While German shepherds and golden retrievers are prone to the visceral (organ related) forms, whippets, dalmatians and bull terrier breeds are prone to the skin forms.

What signs might my dog have?

The signs depend on where the tumour is.

Haemangiosarcomas of the skin usually appear as a small red or bluish-black lump. They can also occur in deeper subcutaneous tissues, often sitting under normal looking skin.

Haemangiosarcomas located in the liver or spleen often grow rapidly, forming cavities containing blood, often only revealing signs when they rupture causing bleeding. This sudden blood loss can lead to weakness or collapse, and is the most common way dogs with this condition present to vets for the first time. Collapse can also be caused by disturbances in the rhythm of the heart, which can happen in primary heart tumours, but also those in the spleen. Occasionally these tumours are picked up early due to swelling of the abdomen or vague signs of illness. Because the tumour and blood loss can cause clotting issues, bleeding from the nose, or another area, may occur.

How will my pet be diagnosed?

The appearance of skin or subcutaneous masses may lead to our vets advising a biopsy, or removal of the mass. Samples sent to a lab can confirm a diagnosis.

With the visceral (organ) forms, diagnosis can be challenging. Dogs we suspect of having a heart, splenic or liver haemangiosarcoma often arrive as an emergency, with severe internal bleeding. Suspicion may be increased by finding a mass via ultrasound scan of the heart or abdominal organs. However benign tumours, malignant tumours (such as haemangiosarcoma), or non-tumours can look similar on an ultrasound scan, but would all carry very different outlooks. If there is evidence of more than one organ being affected, metastasis is suspected, increasing the likelihood of haemangiosarcoma. There is currently no concrete way of confirming the mass type until tissue samples are examined after surgery. A recent study showed that 63-70% of dogs that present to the vets with abdominal bleeding (not caused by trauma) have haemangiosarcomas.

Occasionally a mass is picked up during an ultrasound scan for a different problem. This gives more time for decision making and surgical planning.

How are these tumours treated?

The skin and subcutaneous tumours can be surgically removed with margins of normal skin. As 30-60% of these tumours will metastasise, it is important to remove them. However they may have already spread at the time of diagnosis. Tumours extending into deeper tissues may benefit from chemotherapy (anti-cancer drugs), or radiotherapy, in addition to surgery.

Treatment of splenic haemangiosarcoma involves surgery to remove the spleen, with an additional option of chemotherapy. These drugs are usually well tolerated but can sometimes have side effects like lethargy, anorexia, vomiting, diarrhoea, and fever. Mild to moderately low white blood counts occur in up to half of dog cases but usually do not require treatment.

Because splenic masses often present as an emergency, decisions regarding surgery often have to be made before a clear diagnosis, and thus prognosis, can be given. Removing the spleen is a major operation and can be risky, with some dogs not surviving the procedure. If the dog is subsequently diagnosed with haemangiosarcoma then the outlook is very gloomy.

Factors such as age, other illnesses and signs of spread must be taken into consideration with decision making. All situations are individual, but for some dogs euthanasia may have to be considered as a treatment option, especially if the outlook is poor.

What is the prognosis?

Skin and subcutaneous tumours, once removed, can be examined to give better information on the severity or ‘stage’ of the tumour. Stage I tumours just affect the skin and are associated with an average survival rate of 2 years, whereas stage II and III tumours that either involve the subcutaneous tissues or muscle have a worse prognosis if treated with surgery alone. Chemotherapy or radiation therapy may improve this.

Sadly haemangiosarcoma of the spleen tends to carry a poor outlook. They are often malignant, and most individuals survive less than 3 ½ months with surgery alone, with very few living beyond a year. If there is no evidence of spread, or tumour rupture, and chemotherapy is used, there is an average life expectancy of around 8 months. If the tumour has ruptured, it can be expected to reduce to an average of 6 months.

Although haemangiosarcomas can be found in many places, the splenic form often creates most difficulties in decision making. Our team will be there to support you, talk you through all of the options, and help you through any difficult decisions. If you have any questions on what you have read, or need more information, please talk to one of our vets.