Hello and welcome to the site! Sorry for your having to go through this. I was in your shoes 2 years ago with my Mom, and 10 months earlier with my Dad. I lost them both to cancer. I had a similar situation, Moms doctor used the big terms, long words, vague descriptions with a lot of "mights" and Maybes involved. When we left I asked, do you understand what is happening, and Mom said, "well, not really, but I guess I have cancer".
I explained the entire thing, in her case she was told 6 months, with or without treatements. So I had to cover that too. A very hard thing to do. You can do it or wait till the apt. with oncologist. But it will need to be done.
Just a note on posting questions on this site. When you have a question that you need help from everyone on the network, click on the questions tab at the top of the page and post it there. Everyone sees the questions there. Posting as an update only people who are following you will see them.
Best of luck to you and your Mom, It's a hard, hard thing to do. Harder than me having cancer 3 times myself.
Thanks for being here, lots of great people here to help.