I don't see any reason you cannot fly - but keep in mind that if you have had your lymph nodes removed, you will need a compression sleeve. Otherwise your arm will swell and hurt like h-e-double l!
Also if you are fresh out of surgery and not quite "healed" you may want to ask your doctor - sometimes "healing" can take a long time before you get an ok just to do the simplest of tasks!
Hope that he/she okays it and you have a nice flight and safe trip!