Confused re: Mum's cancer

Can someone explain what i've been told about mum's liver cancer?

So, my mum was diagnosed with liver cancer in September last year. She said they told her she had one tumor and a cyst, but they didn't biopsy it because there was a bleeding risk. So they don't know what kind it is etc

She was put into a trial for a med infusion, and has been going up every 3 weeks. She got surgery today where they said they wanted to see if the infusions shrunk the tumor at all, and they wanted to get the whole thing out, plus a bit around it for safety sake, which i think they did.

My dad said today that the doctor said it could be weeks before they know what kind of tumor it is, so dad seems to think it may not be cancer after all? But would they have given her the infusions if they thought it was benign? I'm basically trying not to get my hopes up in case it turns out dad just got the wrong end of the stick and she actually does have cancer. I can't ask a tom of questions because I don't want to overwhelm dad, and they're in the UK so I can't go there to talk directly to him.

She's 75, I don't know her height or weight, i think she was on blood thinners but stopped them for the surgery.