Hi,
When it comes to lumps in young men, most often there is no particular explanation and it's entirely harmless.The lump is often tender and can sometimes occur in both breasts.
At your young age,breast cancer would be very rare indeed..but one can never be too sure about the nature of these lumps unless more investigation is done.
It could be an enlarged breast bud or gynecomastia,which are a common condition in your age group.
Even though your doctor told you that there is nothing wrong with this lump,you seem to be worried about it ...In that case,I would advise you to take your mammogram/ultrasound reports/films to a breast specialist for a second opinion who might recommend some form of biopsy,removal of the lump or just keep an eye on it.
Best wishes....
You mention having been to Dr.s ..... if one of them wasn't a Breast Specialist you might try seeing someone specializing in breast issues. These lumps in younger males are usually related to hormonal changes and do go away in most cases. I see no reason why you couldn't have this lump removed if it causes you discomfort or even constant concern. Regards .....