Hemangiosarcoma in Cats

Hemangiosarcoma (HSA) is an aggressive, rapidly growing malignant tumour which arises from the endothelial cells which line the interior surface of blood vessels and help the blood to flow smoothly. It is more common in dogs and is thankfully quite rare in cats with an incidence of 0.3-2%. There is no breed or sex predilection; however, pale-skinned cats have a higher incidence of dermal hemangiosarcoma, especially cats with chronic sun exposure. The average age is 10.

As hemangiosarcomas are a cancer of the blood vessels that are found throughout the body, tumours can develop anywhere.

Types of hemangiosarcoma

  • Dermal (skin)
  • Hypodermal (beneath the skin)
  • Visceral (affecting the organs)

The skin, liver, heart, and spleen are the most common locations. Visceral hemangiosarcoma has a higher incidence of metastasis; common sites of metastasis include the heart, liver, brain, spleen, and lungs.


Symptoms can vary depending on the location of the primary tumour and if it has metastasised but can include the following:

Dermal and hypodermal:

  • Single or multiple masses which are firm, raised and dark. The most common locations for dermal hemangiosarcoma are the head and rear legs.
  • Soft or firm masses underneath the skin.


Because hemangiosarcomas originate from blood vessels, they contain blood, which can easily cause the tumour to rupture. Often the first sign that the cat has a hemangiosarcoma is when this occurs, and the pet collapses. Rupture can cause fluid in the abdomen or thorax, organ dysfunction or disseminated intravascular coagulation, a life-threatening condition where tiny blood clots form throughout the body.


Your veterinarian will perform a complete physical examination of the cat and obtain a medical history from you.

Diagnostic workup:

Baseline tests: Complete blood count and biochemical profile. These can evaluate the overall health of the cat and may reveal low blood platelets or anemia (low red blood cells) and fragmented red blood cells (schistocytes) or nucleated red blood cells (metarubricytes) if the spleen is affected.

Biopsy and histopathology: A definitive diagnosis is made by biopsy, which will be evaluated by a veterinary pathologist.

Abdominal and thoracic imaging: To look for tumours on the abdominal organs and/or signs of metastasis and evaluate for fluid in the abdominal cavity.


Surgery: Removal of the tumour with a wide margin is the treatment of choice. Dermal and subcutaneous tumours are easier to remove than those on the organs and have a better prognosis.

Splenectomy: Complete removal of the spleen. This alone gives an average survival time of between 1-3 months; the addition of chemotherapy can increase the survival time by a further 1-2 months.

Chemotherapy: As a follow up for cats who have had a tumour surgically removed or as a standalone treatment for cats with a tumour that is inoperable.

Supportive care: To manage symptoms, which may include fluids to treat dehydration, blood transfusion, analgesics (painkillers) and nutritional support.


Cutaneous and subcutaneous tumours without muscle involvement have a mean survival time (MST) of over 1,000 days. Unfortunately, the survival time for visceral hemangiosarcoma is considerably shorter.