I am sorry to hear that Chloe is so sick with liver disease and other complications. She is only 9 years old; that is young to be so sick.
My name is Rebecca. I am a veterinarian and will do my best to help.
It would help if you have copies of the blood tests, the actual numbers. Since I can't see and examine her, the more information I have, the better. For instance, it would help to know what her albumin level is since that gives us an idea of liver function.
I see she is bleeding into her abdomen. If they could use ultrasound to get a sample of the blood in her abdomen for microscopic analysis, that might tell if the bleeding is from a tumor or not. Cancer cells might be seen, if they could get some of the fluid.
Did they miss the tumor on the first ultrasound? Possibly, but it may not have been there then, or may have been smaller and harder to see.
If there is a tumor on the liver, has it been there and getting worse for 4 to 7 weeks? That is possible as well. Seeing that biopsy report from the original ultrasound would be helpful for me to tell you more.
Yes, a tumor could have developed and ruptured that rapidly.
Have the ultrasounds examined her spleen? It is next to the liver, and also can develop tumors that rupture and bleed into the abdomen.
Chloe sounds very sick, and I think your vets are being fair and honest to give you a guarded prognosis. Cirrhosis often does not get better, and now it sounds like there is concern about her having cancer. I am so sorry. You must be so worried. Please let me know what other questions I can help with. Rebecca