Dear df: This lump could be a variety of things, from an ingrown hair or abcess. It is unlikely, at your age, that this is breast cancer. Your doctor, after examining you and reviewing your history, may be able to diagnose the problem. However, the only way to know for sure is to biopsy. Since the lump can be felt, it may be possible to do a needle biopsy. In some cases, though, it may be easier to remove the lump entirely.