my 4 legged boy (dog) had an ultra sound that showed a mass on his liver. I'm trying to find the least invasive method to determine what it may be, malignant or benign and if it should be removed or left as is. 10 years old

You should have further tests on that mass... CT scan, etc. The best place is UCD; they will have a consult with you whether to remove the mass with laparoscopic surgery or something more significant. Do not wait.

Tried but they aren't taking new patients with his type of issues. I need to wait a month and try again or try somewhere else for now. I'm going to try somewhere else and see what they recommend. Disappointed!

Yes, do not wait...Uc Davis saved my dogs life more than once. Other vets misdiagnosed my dog and Uc Davis got it right. Its cheaper in the long run to go to Uc Davis as they get it right the first time and have the means to do all procedures there