This tumour type is situated in the skin or subcutaneous tissue (especially the lighter-haired areas or the skin on the belly or foreskin with few pigment).

Behaviour

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. Therefore, this tumour type is discussed according to its location. In general, small tumours and those that are well defined in the skin have a better prognosis than the other tumour forms. Hemangiosarcomas represent 2% of all canine tumours.

Breed predisposition

A higher risk of developing this tumour type has been reported for Border collies, Dalmatians, German Shepherds, Golden retrievers, Hungarian wirehaired vizsla's, Labrador retrievers, Dachshunds and greyhounds vs other breeds.

Symptoms

Superficial tumours behave less aggressively than those invading the subcutaneous tissue and muscles. The tumours of stage II and III are typically large, poorly defined and look like a bruise.

A biopsy (histopathology) is absolutely necessary for the diagnosis. The evaluation of the stage of the tumour is based on the depth of the tumour (stage I: dermis, stage II: subcutaneous tissue, stage III: reaching the muscle). A blood analysis and chest X-rays are advised to assess the presence of metastases.

A large surgical excision and supplementary chemotherapy are advised. Chemotherapy can decrease the size of the tumour and allow surgical excision this way (this option can be necessary when tumours are too big for surgical excision). When a tumour is eliminated via surgery, margins (space around the tumour) of 1-2 cm are generally enough.

Stage I hemangiosarcoma of the skin: total surgical excision is possible up until 78% of dogs. In 30% of cases metastases are present (limited to the skin at a certain distance from the primary tumour). The survival has an average of 780 days.

For stages II and III, only 23% of tumours can be completely excised because these tumours are bigger and less well-defined (= more difficult to distinguish from the surrounding tissue). For stages II and III, 60% metastasizes towards the lungs, the local lymph nodes and distant parts of the skin. The survival time for these dogs is between 172-307 days. When stage II and III are thoroughly treated (surgery with possibly supplementary radiotherapy), supplementary chemotherapy can lead to a significant increase of survival (for subcutaneous hemangiosarcomas 1189 days; for intramuscular hemangiosarcomas 273 days).

The more the tumour invades the subcutaneous tissues, the worse the prognosis.

In subcutaneous or intramuscular hemangiosarcomas, local recurrence occurs in more than 20% of cases and metastases occur in 42-75% of cases. The median survival time after treatment with surgery and chemotherapy is approximately 1-1.5 years. If treatment is limited to surgery, the median survival time varies between 172 and 307 days. For chemotherapy alone, the median survival time is approximately 133 days. For palliative radiotherapy, the median survival time is approximately 90 days.