In the midst of life.... in blackpropaganda

You know that if one of your sons rings you at 8 am in the morning then there is something wrong.
He had had a text to say that the wife of one of his best friends had died of cancer in her early 40s.
We went to their wedding - and she had treatment then, and then was little possibility they could have children - but by a miracle they had a girl - and their happiness was complete.
Apparently the cancer returned, and it was progressive over the last few months - but it was kept very quiet.
What can you say?
I shall paint a card to offer our sympathy - and say the right words - but what a crushing blow in the midst of life.