By Nan Talleno

PHILADELPHIA (CBS) – Hemangiosarcoma is an unusual and rare type of tumor that originates in cells that form blood vessels.

Also known as HSA, it has been seen primarily in larger breed dogs (not always but oftentimes in lighter pigmented and/or short-haired breeds) and also in horses, sheep and even cats. Unlike lymphoma, which can affect both humans and animals, hemangiosarcoma is a cancer that does not affects humans.

It can occur on or under the skin, also on the lungs, the kidney, the liver, the spleen, muscle, bone or even parts of the eye and the heart can be affected.

If affected on the skin, it may appear as either a reddish or possibly a bluish black growth. When it is confined to the skin alone, it may be less likely to spread. Unfortunately it is more difficult to detect symptoms early on in other affected areas.

Likely symptoms of HSA may include weakness, lethargic behavior, increased heart rate, weight loss, abdominal swelling, increased and/or excessively rapid breathing, labored breathing, pale gums, exercise intolerance and in advanced stages, possible seizures or even collapse.

In severe cases, dependent upon its location, this tumor can be life threatening resulting in sudden death.

Symptoms may not present themselves right away, so it’s important to receive a good examination and a clean bill of health from your vet.