I have a 9 year old GSD with spleen issues?

I have a 9 year old GSD i took him to the vet and he has anemia so he had a scan today of his spleen which showed a shadow on the spleen. Please can you advise me what this shadow could be? i know that with out seeing the animal this is difficult. He is showing the following symptoms: Weakness resulting in collapse then recovers and seems fine, loss of appetite, quicker breathing, has had distended abdomen. i do not want my old dog to go through unneccessary exploratory procedures but if you could give me an indication of how i can make him more comfortable as pain free as possible (the vet has said he is not in pain at the moment.) thank you