Many times I get asked if the gynecomastia will return. The short answer is no. And this is because I will be removing 99% of the gland in the affected region as well as significantly reducing the fat in area as well. As a result, the remaining gland cells simply do not have the capacity to grow back to what they were before the surgery.
Of course as I leave some fat cells behind, if you increase your consumption of food beyond what your body requires then the excess calories floating may deposit in the chest area again leading to some enlargement, albeit fatty and not glandular enlargement. So keeping steady with your diet is important afterwards.
The long answer would also state this may not always be the case and that glandular regrowth may rarely occur. In fact in the last 20 years I have actually seen the gland grow back in only three individuals. Two of them however confessed to using anabolic steroids which stimulated the remaining gland cells to increase in size and thereby leading to a recurrence.
The third individual however denied any steroid use, so I cannot fully explain why this came back on him, and only on one side. However just to put this into context I have done well over 1500 gynecomastia surgical cases in my career so these cases represent a tiny proportion only.
The fact remains that with medicine and the human body no one can therefore offer any concrete guarantees, although it is extremely unlikely for it to come back.