Haemangiosarcoma (HSA) is a common disease in dogs.
The most commonly affected site is the spleen, followed by the right atrium, skin and liver.
Visceral and cutaneous haemangiosarcomas are evenly distributed in cats. 70% of patients presenting with a non-traumatic haemoperitoneum are diagnosed with haemangiosarcoma.
Two thirds of splenic masses are neoplastic and of these, two thirds are haemangiosarcomas.
Surgery is only palliative because 80% of patients have micrometastatic disease at presentation (this does not show on conventional and advanced diagnostic imaging), therefore adjuvant chemotherapy is indicated after surgery except for tumours confined to the dermis