According to the Golden Retriever Health Survey, conducted in 1998 and published in 2000, one in five Goldens will develop hemangiosarcoma of the spleen, a malignant form of cancer.
In addition, one in eight Golden Retrievers will be diagnosed with another malignant cancer called lymphosarcoma.
According to Amy Haase, DVM, writing for Suite101.com:
"Current theories about Golden Retrievers are increasing suspicion that this breed may lack a genetic ability to repair damaged DNA over a lifetime, thus explaining the increased tendency for lymphoma and hemangiosarcoma."
Splenic cancer is silent – evidence that a dog has the disease does not appear on routine blood tests taken to screen for other illnesses like liver or kidney disease. However, an ultrasound can help vets visualize problems with the spleen.
Per Dr. Haase:
The spleen is easily visualized by ultrasound, and normally appears as a very bright organ with a smooth, bright white and thick capsule that defines it well from other organs in the abdomen. Tumors will appear in various forms, but the most common and alarming appearance is a large irregular mass with multiple black cavities of blood divided by thin walls of tissue. These are the tumors that are at high risk for rupture and fatal bleeding.
Dr. Haase recommends that in breeds at high risk for splenic hemangiosarcoma, regular ultrasounds of the spleen should start at around age five and be repeated at least yearly. Ultrasounds are non-invasive, without side effects, and are well-tolerated by most pets
In addition to regular ultrasounds, it is also recommended that high risk dogs be seen by a vet every six months for a careful palpation of the abdomen to check for any abnormalities or changes.