It SOUNDS like your Dr. is right and it's not cancer as your liver enzymes really start going out of whack quickly when its hit like that, but this is one case where if he's wrong and you wait very long at all (even a few months) you WILL DIE. So go see a specialist and either do a biopsy or insist on RFA or Targeted Radiation therapy to either burn out the cyst or kill off the tumor whichever it is if you think there is a chance it could be cancer.
Most likely it is indeed just a cyst and your Dr. is worred that any invasion will harm an already weakened liver and cause more damage then its worth - but YOU need to be the one to make that call, and you need to research and know what you're dealing with so you can make an EDUCATED call. Lots out there on the web ... and while I'm not a Dr. I "Play one" since starting to fight my liver metastases some 26 months ago!