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A lump that is getting larger could be a lymph node, a cyst, a lipoma or an abscess deep within. In males chances of breast cancer are less but should not be ignored. Ideally you should consult a surgeon for your son. However you can go to the PCP and maybe get a CT scan for the lump followed by a surgeon’s appointment.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
It can also be an extra breast tissue that is growing.