Name changed for this.
Backstory is that my husband works away for 4 months at a time and is currently halfway through his current trip (i.e. has another 8 weeks to go).
MIL called me yesterday to tell me she has been diagnosed with breast cancer but it has been caught very early and all being well she will have surgery to remove it and that will be it over.
She has asked me not to tell DH (her son) as it is hard enough for him working away for such long periods without adding in the stress of this too.
I don't know how I feel about keeping this "secret" from him but also, it's not my secret to tell. I feel like I can't win either way. If I tell him then MIL will be annoyed and if I don't then DH will be annoyed that I didn't tell him (at least I think he would be... Or maybe he would agree I was right not to tell him as she asked me not too).
Everyone else knows, his brothers, his cousins etc so he will be the only one who hasn't been told.
I have no idea what to do... Any advice gratefully received!