Sorry to hear your wife has breast cancer.
Best wishes for a speedy recovery for her.
In tough times, sometimes it is good to have something more pleasant to look forward to - like tennis.
I'm sure your wife will be given post-operative range of motion arm exercises because of the discomfort encountered with arm movement early in the post-op period.
But is there a little time before her surgery?
One of the current concepts in those undergoing surgery is "pre-hab".
Basically this is starting rehab therapy before the procedure has occurred.
It will lead to a quicker recovery, both because the patient is slightly stronger, but largely because the exercise patterns are already known.
If you wife is not already doing the thrower's ten exercises, now would be a good time to start, providing she is in the proper frame of mind to do so.
Thrower's Ten Exercises: http://www.muhlenberg.edu/pdf/main/a...throwers10.pdf
It is also natural to have periods of feeling "down" and "anxious" both before after the surgery.
Many physicians are advocating "exercise therapy" as a way to stay fit, take your mind off other problems, and even sleep better.
Using an exercise bike would be an example of a fitness strategy that could be started relatively soon post-op.
Again, sorry to hear you both will be going through all this, but if future tennis enjoyment is a motivation for a quicker recovery, that's great.