Hello Beckie (can I call you Beckie - is that your name?).  So sorry about your grandad.  I remember the special bond I had with my own maternal grandfather; like many he had the time to sit me on his knee (when I was little!) tell me silly stories and read to me from The Broons and Just Wullie annuals.  My nana (I called them by the same names as you do) used to tut-tut affectionately at his fund of stories.  You never forget these things. 

I can imagine you are in a state of shock having been thrown into a strange and horrible new world of which you know little.  What care is your grandad getting?  Is he at home?  Is he getting any treatment?   Have the family got information about the likely progress of his cancer?  You need to know these things so you can all work together to help him.

I think you need to know what is happening then treat your grandad as you have always done, with love but don't suddenly overwhelm him with your emotions as he doesn't need to be stressed by everyone else being stressed!  Easier said than done, don't I know it.  By all means let your tears out and lean on friends for support, you need to have an outlet for your worries.

I have not had cancer but am here because I lost family members and friends to cancer and I hate the rotten disease; it's a beast.  So I hope others of the knowledgeable and caring people who post here will come and chat with you also.