I would definitely advise staying away from Dr Google: the info that comes up on such searches is rarely helpful and always a worst case scenario. Try to wait to speak to someone at the surgery or hospital if you can.  It's hard not to search for information, I'm so guilty of it too, but the only useful info I have had groom the web has been on here, from real people. 

Amanda Jane - I'm so sorry to hear about your Mum and outraged at the way she was informed.

The first thing you both need to do is first thing in the morning phone the doctor who ordered the test, tell him or her what has just happened and firmly ask for more information and an emergency face to face consultation. If you can't get the doctor ask for his or her medical secretary and explain the situation.

I also strongly recommend making a formal complaint in writing to your hospital, this was completely out of order and was about as far from best practice as it is possible to get. Frankly whoever made that call needs sorting out and prevented from doing it again.

As reb82 has said, there are so many permutations of cancer type, stage, grade etc to be able to offer any useful advice, apart from try to be as calm as you can and get the information, support and advice you and your Mum need and are entitled to. 

Good luck
Dave