I'm SO sorry to hear you are going through this. I am not an expert by any means, but we lost our 7-year-old GSD to Hemangiosarcoma last year. He was fine until the morning he seemed off and by the end of the day could not make it to the barn with me to feed the horses. To make a long story short - we took him to an e-vet, who said he had massive internal bleeding. Rather than do the surgery, we elected an ultrasound first. That showed a spleen that looked like it was covered in freckles. Lots of small tumors all over it and suspicious (though unidentifiable) liver lesions. His heart was fine and clear. I was there and saw it and the US doc said that while he could not do a definitive diagnosis without biopsy, it was classic metastasized (through the spleen and possibly liver) hemangiosarcoma that he had seen many times before. I don't know if hemangiosarcoma sometimes presents with large tumors, but do know that in our case, it was many, many small ones.
We were presented with options to remove his spleen - but have to put him down on the table if it was indeed in his liver - and then to do chemotherapy. In any case, the prognosis was just a few months. We elected to not do any of these and to let him live whatever life he had left. We put him down at the next major bleed, which came a few weeks later. He had a lot of good time during those weeks, with minor bleeds occasionally. Our vet assured us there was little to no pain - just weakness from bleeding out.
I would be guardedly encouraged by the size of the tumor - but again - sure am not an expert - just sharing our own recent experience, which is much different.
I hope the results come back very soon - the waiting is the worst! Please keep us posted and let us know how things are going. In the meantime, hopefully he will be home soon and you will be able to spend some good quality time with him.
We're with you!
Luther GSD 3/18/08
Otto Mix Spring 07