You poor thing! I know how jittery you feel to any minor comment, letter or phone call , or even just 'how' things are said at this time! I can see why a letter like this would be distressing with no communication prior to it from a breast cancer nurse or oncologist. I think you should ring your BCN nurse right now, and ask for some answers, as the current fear in your head, and going in circles of 'what is it' , must be worse than actually hearing facts. Maybe someone will come along shortly who had a chest X-ray after surgery ( I didn't) but I have heard on here that sometimes they are done as matter of course just to be sure there is nothing else that has been missed (depending on the position, size and type of BC removed), it doesn't mean there definitely is something to worry about. I know this probably won't help you feel any better, but do ring someone today if you can to get some answers.
C x