thanks Mirren, they have said that it appears not to be serious and (hopefully) nothing to worry about it atm. have another comparison scan in 6mths time and if no change they will kick me out the door
the question I would have liked answered was, what was it and how did it come to this but they don't know its just one of those things
just have a newly found cavity in a lung which just by chance it was noticed. anyway the doctors comments are half reassuring, now just get back to a normal routine with much less concern
thanks to everyone for your thoughts