This is a type of cancer that German Shepherds are predisposed to, along with Golden Retrievers and Labradors. Often the cancer is found on an emergency basis after the spleen has ruptured. The spleen is an organ filled with blood. When it ruptures, your dog can bleed dramatically into the abdomen, which can result in the dog going into shock. What you might see is your dog being more lethargic than usual, breathing a bit differently, maybe their abdomen looks a bit fuller and the gums are often paler. This is an emergency as your dog can lose a lot of blood and the treatment is to have the spleen removed in surgery. Sometimes a blood transfusion will also be needed to stabilize your dog.
What makes this situation hard, is that a non-cancerous disease called splenic hemangioma can present exactly like the bad splenic hemangiosarcoma. Both need emergency surgery to remove the spleen. However, with the non-cancerous type, the dog will be fine as long as they do well in surgery and post op. With the cancerous type, the prognosis isn’t good for long term survival. So, when faced with a decision to do an emergency surgery, you and your vet do not know if it is going to be a good prognosis or a bad prognosis. Screening for other cancerous lesions like tumors in the chest or seeing tumors in the liver may be of some assistance when deciding whether to pursue surgery for your dog.