Hemangiosarcomas are tumours that originate from blood vessels. The tumour is composed of cells that delineate the blood vessels and that have progressed into cancer cells. This tumour can be cutaneous or subcutaneous, but can also be found in organs such as the heart, the spleen and the liver. Depending on their location hemangiosarcomas have a different behaviour (more or less malignant). The biggest difference is present between (sub)cutaneous vs other locations. In general, small tumours and those that are well defined in the skin have a better prognosis than the other tumour forms.

Behaviour

This tumour is particularly aggressive, and metastases are often already present at the time of diagnosis. This tumour can have various forms: the size can vary, it can be pale gray or red or purple, soft or gelatin-like (it often contains zones where the tissue is filled with blood or is necrotized). These tumours are in general ill-defined, non-encapsulated and often attached to other organs. A hemangiosarcoma is a very fragile tumour and should therefore be handled with care. Manipulations can lead to rupture and abdominal bleeding, as well as spreading of tumour cells. These bleedings often occur spontaneously.

Prevalence

This tumour type is mostly seen in middle-aged dogs, but can also manifest itself in dogs younger than 3 years of age.

Bfreed predisposition

A higher risk to develop this tumour type was reported for German Shepherd, Golden retriever and Labrador retriever vs other dog breeds.

Symptoms

The symptoms depend on the tumour location and can be very varied. It is possible to have symptoms of discomfort, swelling of the abdomen without other symptoms, but also sudden collapse and death due to major bleeding.

A common symptom when the hemangiosarcoma is situated in the abdomen is a sudden weakness or collapse. This can be preceded by temporary episodes of weakness from which the dog recuperates spontaneously within 12-36h. Other vague symptoms that may occur include weight loss and a lack of appetite.

When the hemangiosarcoma is located in the heart the dog will be easily tired, will have more difficulties breathing and have an accumulation of free fluids in the abdomen.

During a physical exam, pale membranes can be observed as well as an elevated heart frequency and possibly an abdominal mass. Heart beats can sound muffled due to the presence of the tumour.

To enable staging the following examinations are necessary: bloodwork, coagulation test, imaging of the thorax and abdomen, ultrasound of the heart and possibly a punction of free abdominal fluids.

Blood analysis

Bloodwork can often reveal anemia and damaged red blood cells. It may be necessary to check the blood type of the dog for a blood transfusion. In 75-97% of cases there is a mild to severe shortage of blood platelets. Specific coagulation tests can show whether there are specific problems present and what the risk of the dog is regarding the development of serious complications.

Punction of free abdominal fluids

The punction of abdominal free fluid will mostly yield a bloody liquid. The examination of the cells present in this liquid (cytology) rarely leads to a diagnosis as this fluid is very diluted and cancerous cells are easily missed.

Radiography and ultrasound

Before surgery, the presence of metastases should be checked (a radiograph of the thorax should always be done). The radiograph of the abdomen can show a mass on the spleen, liver or other parts of the abdomen. Abdominal ultrasound is necessary to confirm the presence of masses. Free fluid in the abdomen can disrupt radiographic imaging, whereas this is not the case with ultrasound. Via ultrasound of the heart the presence of a tumour on the right heart ear can be checked (present in about 9% of dogs with a hemangiosarcoma).

Biopsy

A surgical biopsy is necessary for the diagnosis. Via histology the tumour type can be determined. When this is not possible based on the appearance of the tissue, multiple markers can be used to indicate what type of tissue is involved (for the Von Willebrand VIII factor or CD31/platelet endothelial cell adhesion molecule (PECAM), claudin-5, CD117).

Staging

Staging system

Stages

Surgery

Surgery is the primary treatment method for hemangiosarcoma. Before initiating surgery, the dog’s blood should be checked for anomalies. When anomalies are present, they should be corrected.

When the tumour affects the muscle, it can be difficult to obtain wide margins and (depending on the location) this can lead to amputation.

When the tumour affects the spleen, the spleen must be removed, and the abdomen checked for the presence of possible other suspect masses in the liver or peritoneum. The removal of the spleen leads in 24% of dogs to cardiac arrythmia. These arrythmias require post-operative follow-up, usually these disappear spontaneously within 24-48h after surgery.

When the tumour affects the heart and causes a pericardial effusion, cardiac function can be improved by removing the whole pericardium or a part of it.

Chemotherapy

Since the risk of metastases is elevated and there’s a bad prognosis when only surgery is performed, chemotherapy is always advised (unless the hemangiosarcoma is limited to the skin). This combination can lead to a survival of 6 months on average. Most of the time a protocol based on doxorubicin is chosen and/or metronomic chemotherapy given (which is a low and frequent dose of cyclophosphamide combined with non-inflammatory drugs).

Radiotherapy

Radiotherapy is rarely used to treat hemangiosarcomas due to the anatomic sites involved and high metastatic rate. Radiotherapy is also used as a palliative treatment, to reduce complaints.

The prognosis depends on the localization of the tumour and the clinical stage of the tumour (the higher the stage, the worse the prognosis).

For a hemangiosarcoma of the spleen or the liver the prognosis is very bad when the treatment is limited to a surgical intervention. The mean survival time is between 19 and 86 days and less than 10% survive more than a year. The tumours in stage I have a better prognosis than those in stage II when post-operative chemotherapy is used. The prognosis for hemangiosarcoma of the heart is similar. For dogs that undergo surgery the survival time is between 1-4 months. The presence of abdominal free fluid or collapses are also linked to a worse prognosis.

For a hemangiosarcoma of the kidney the prognosis is better than that of other organs in the abdomen. After surgery it is advised to do chemotherapy. This will increase the median time of survival to between 141-179 days. Unfortunately, even when chemotherapy is added to the treatment, only 10% or less of dogs live longer than a year.