<s>[INST] My 12 year old son has a lump under is right nipple, he says it is sore I am concerned because it is bigger than a quarter. What should I do? My first thought is it is probably puberty but I am thinking now I should make an appt. With his pediatrician [/INST] Hi, dairy have gone through your question. I can understand your concern. Your son may have gynecomastia.  It is common at pubertal age.  You should go for examination.  If needed go for fine needle aspiration cytology of that lump.  It will give you exact diagnosis. Then you should take treatment accordingly. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using Chat Doctor. Wish you a very good health. </s>