Need help

I think you should say you have heard of her illness and offer to help if needed. Just give them an opening to talk about it if they want to. Don't over think it all, we all have different ways of dealing with illness. Let them know they have your support and then step back.
I hope your daughter in law makes a full recovery.

I never told my mother anything serious and worrying if I could avoid it as she was such a worrier and the burden of her worry could be too much to bear at time when I was already stressed.

Could this be you, Kartush?

Perhaps they don't want you to worry. My DiL is very seriously ill. I'm never updated on her everyday treatment. I don't know from one day to the next what's going on. She wants to pretend everything is fine. She's found a place inside herself were she can contain all her emotions. We have no option but to respect that but it's very very hard. In someways it would be much easier to know what we're dealing with. It isn't that she doesn't care about our side of the family, quite the opposite she loves us but it's important to her that everything is kept as normal and ordinary as possible, mostly I think for the children's sake. Can you get your son on his own and ask? I've done this but I don't make a habit of it. I don't want him to feel overwhelmingly bombarded with questions. My last conversation about it a few months back was" just because we don't ask doesn't mean we don't worry and just because we worry doesn't mean you can't come to us" I hope your dil has a complete recovery. It's normal for you to worry and have a minefield of emotions but don't take not being told personally. It's not because they don't care about you and it's not because they don't value your love, they do. Have a quiet word with your son and respect how they need to handle this in the coming weeks or months. My heart truly goes out to you in this difficult time.

I agree with Jane10 be open about it with your son Say there are lots of rumours flying around and you would like the truth. Are you naturally a worrier could it be that they are keeping you out of the loop in the hope of getting used to the news themselves or to protect you
I do think it's a mistake to tell some people and not others but ask your son outright and don't take it too personally that you weren't told at the start

Cancer isn't always life threatening try and stay positive

I agree with mumomb. I really feel you are overthinking it.

Is it possibly Chinese whispers and putting two and two together to make five? Be direct with your son. Ask him if the rumours are true. That could also alert him to the possibility that the news is all round the neighbourhood.

So why didn't you say that it was cancer in your opening post?

Perhaps they were trying to protect you from worry over Christmas? Could you ring and say to your son you had heard A is ill

and can you do anything to help and see if he is forthcoming? Was the niece sworn to secrecy or are they letting the news slowly filter out? A lot of cancers are treatable now. If it was me I would ask. Hope it all turns out ok

Problem is, it is cancer

Your son has said it's nothing to worry about. Presumably had it been something to worry about you'd have been told.

I often find my son, or daughter or SiL or DiL has been ill after the event.