Your wife's pain may be due to irritation/disruption of the very rich nerve supply that goes through the breast and underarm. Unfortunately some surgeons are not very knowledgable about this problem ( and others) - they seem content to say, "oh, it's normal to have pain after surgery" and not offer assistance in dealing with the very real problems of healing.
I suggest you take a look at Dr Susan Love's Breast Book, 4th edition - would be well worth purchasing. Dr Susan Love is an expert physician and researcher who has herself survived breast cancer, and is highly dedicated to helping women navigate as easily and painlessly through this experience as possible, as well as to recover and maintain breast health. You will find the answers to many questions there - including suggestions on how to deal with doctors who are not giving the support that is needed.
Sincerely,
Tre