- Chosen by Voters Courtney – At 16 years of age, your chance of having breast cancer is almost zero. More likely your breast tissue, closest to the nipple is normally developing into adult features. What puzzles some young ladies is that one breast may start enlarging before the other so that at first one lump only is felt. There are several possible, but less likely causes of benign lumps in the breast, including a benign fibroadenoma nodule, a benign cyst, and even a deep skin benign tumor, including a lymph node. My best guess = developing normal breast tissue. Have your doctor check it out on your next visit. Source(s): a medical professional 2 years ago 67% 2 Votes