A 14-year-old boy presents with the complaint of breast swelling. The boy reports that he has been in good health and without other problems but has noticed over the past month or so that his left breast has been achy and that he has now noticed some mild swelling under the nipple. He has never seen discharge; the other breast has not been swelling; and he denies trauma. Your examination demonstrates a quarter-sized area of breast tissue under the left nipple that is not tender and has no discharge. The right breast has no such tissue. He has a normal genitourinary examination and is Tanner stage 3. Which of the following is the best next course of action?
a) Observe for resolution
b) Begin testosterone therapy
c) Obtain mammography
d) Perform fine-needle aspiration