Ideally, gynecomastia surgery is delayed until full development, around age 18 after adolescent hormonal influenced breast development ceases. Sometimes it will resolve to a degree afterwards. Also if your child is overweight, often the breasts will diminish with weight loss once in the normal range. However I have operated on several adolescent males to develop gynecomastia for those stigmatized and traumatized by the size of his breasts in severe cases with good results. Yes it is possible they will grow again and another procedure may be required for best results, Discuss the risk vs benefits with your board certified plastic surgeon that has experience in this age group.