Well this is a new one...You have me wondering too. She is YOUR WIFE for god sakes...Ask her why she is hiding her bosom from you. I don't know why people on here want you to "trick " her into talking to you, that is so immature.
I am sorry but those suggestions are ridiculous. I have had 2 lumps removed, but I never hid the fact from my husband. Just ask her. If more married couples talked to each other, openly, we would have a lower divorce rate.
You have every right to know.
If she has had a lumpectomy, or something similar it would not be unusual for her to feel ugly and want to cover up.