At your age, you need to get a mammogram (which is an x-ray of the breast) and an ultrasound examination done to evaluate the lumps in detail. From your query, I understand that the lumps must have had a needle biopsy. Although they are benign, as you have mentioned, only a detailed examination and above mentioned investigations will give a clue as to their exact nature. There is a small possibility that a benign lump in the breast may in course of time become cancerous although the risk is low. In your case, it is best you consult a surgeon or an oncologist and after the above investigations, they will probably advise you to have the lumps removed.