You've probably seen the news already, but this came as a shock to most, even though we knew he had been in hospital for a prostate problem. The cancer was only discovered because of that and his reaction was typical of the man - for other men to be aware and to get their prostates checked out.
But this is different and Buckingham Palace has not given any further details, but I'm sure that it will in time, bearing in mind that Charles appears to be much more open than his mother was in this respect.
It must be frightening and I hope he makes a full recovery.