I'm not 100% certain on this one but I know enough to question his doctor.
In order for them to say that this cancer originated from another location tells me that they should know where his cancer started.
Cancer cells that they have recently found should tell them or the pathologist where it all began.
It could be that it started in the lungs and moved onto his liver and bone or maybe it started in his liver and moved to the lung, etc.
They SHOULD know what type of cancer he has. He could always ask for a 2nd opinion.
Are these the only three places that he has cancer?
Your father is young (same as my dad)...
~Zig