Hi BM, I've no medical knowledge but have been and am going through this treatment for Breast cancer right now, the one thing I know when I have the lumps, is, the lumps or pre diagnosis never has pain, a surgeon oncologist once told me, that the mass itself doesn't cause pain, it is all the treatment after to remove it, that said, I would advise anyone with any change in their breast get it checked out, just to rule out the big C as you say, and get a definite diagnosis of a cyst or whatever - I do hope she gets seen to soon and it is just as you suspect, a cyst. if they happen to her on a regular basis, tell her to keep note, could be hormonal. Best of luck to her x