how would you react to this situation?

If everything's fine than i must say that your uncle is a great man who handled everything so nicely and so quietly not making her understand the pain of a cancer paitent, and the fear and scare of it

Salutes to your uncle! now thats how we say, dont wanna hurt you and take away all your pain

I hope your aunt is all fine now!

I would say that the matter is between the aunt and uncle and not really anything to do with your friend. She has not been the one with cancer nor the one taking care of her aunt (I assume). The uncle may have felt that the aunt could not cope mentally/emotionally with the knowledge of having cancer and he would then have had to deal with so much more. The fact that the doctors told the uncle and not the aunt would suggest he was right.I'm sure its not a decision he has taken lightly and he will probably tell her at some point if he feels she can cope. Being told that you've had cancer and come through is probably better than having the shock and worry of knowing or even thinking it at the time? I would not be surprised if the aunt has worked it out for herself and, by not mentioning it,feels that she has saved her husband from worry. Hope her health is improving now.