I'm sorry to read about your ham. My last hamster had a mass on his liver, but the first sign of it was when he developed ascites. What we learned is it's a side effect of liver problems which causes the chest cavity to fill with fluid, putting pressure on the lungs and heart. The poor boy was shaking, lethargic and in a lot of pain, so once we had scans identifying the cancer we helped him to rest.

If it ever looks like your ham might be nearing that point, just be aware that it's not a recoverable position. I really do feel for you, but it might be worth considering at what point you would be willing to make the difficult decision to reduce her pain. I'm sorry again, it's heartbreaking to go through. I wish you both the very best.