This is most likely a benign lump termed gynecomastia I have never seen one
on these that are malignant on a man but they can be.  If the man has a
family history of breast cancer there may be reason for more concern.  Most
men decide to have them removed for peace of mind and sometimes for
cosmetic reasons.

You should also be aware that this can be a sign of steroid use. I am not
saying this man uses steroids but the weightlifter history does make it
something to consider.  All the men I have seen with this problem have: 1)
Been Benign  2) been non athletes so it can occur in any male.  It is often
noted a puberty in the male also and will often get smaller then.

Jon Ahrendsen MD FAAFP
Clarion, IA