This tumor is particularly aggressive, and metastases are often already present at the time of diagnosis.
This tumor 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 tumors are in general ill-defined, non-encapsulated and often attached to other organs. A hemangiosarcoma is a very fragile tumor and this is why it should be handled with care and one should avoid manipulations that could lead to its disintegration and spreading of its parts. Another consequence of their fragility is that they rip open easily which leads to abdominal bleeding.
This tumor type is mostly seen in middle-aged dogs, but can also manifest itself in dogs younger than 3 years of age.
A higher risk to develop this tumor type was reported for German Shepherd, Golden retriever and Labrador retriever vs other dog races.
The symptoms depend on the tumor 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 tumor.