Hard lumb under breast

This is an issue with my son.  He is 14 and going through puberty.  Today he told me about a lump he had just found.  The lump is under his left breast.  It is small, hard, and hurts if pressure is applied to it.  I am currently undergoing cancer treatment, and have previously had breast cancer 4 years before.  Please tell me what this could be.

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Dear helpme101:  Breast cancer in men is very uncommon and in young boys, practically unheard of.  However, the general rule of thumb is that if there is a lump, it should be examined by a physician to determine if further evaluation is necessary.  Breast changes are not uncommon in boys going through puberty.