My dad also has cancer. His is non hodgkins lymphoma and he has been through chemo successfully twice now. His cancer is not curable, but if treated and in a place that is treatable it will go into remission for periods.
There are many cancer survivors in this world, so until you find out otherwise assume your mom will come through this. Chemo and or radiation are ugly, but better than the alternative. The more positive an attitude she has and the people around her have, the better off she will be. It is tough, I know, I used to come home and break down in tears after being at the hospital.
Do as much research on knowledgeable sites that you can. By this I mean sites like the Canadian Cancer Society, etc. <not sure what it is in USA> Avoid just doing a blanket search for cancer.......it may scare the crap out of you and half of it isn't true!
Talk to the doctors. Ask all the questions you have. You may wish to prepare a list so you don't miss anything. Bring a pen and paper to write down anything you may want to research or don't think you will remember.
Last, hang in there and be strong. Until you know exactly what you are dealing with there is no point in panicking. <easy to say i know!>
I'm sorry you find yourself in yet another club of mine

Sometimes God works in myseterious ways for sure!!
Hugs
Kid