I am 54 yrs old. I had my first fibroadenomas, the most common type of benign breast lump, removed when I was 17. I have had 8 removed over the years and I am followed closely by two breast specialists, one of whom I use for second opinions, mainly because of the prevalance of breast cancer on my mother's side of the family (mother, grandmother, aunts and cousins).
I have decided to let go of the "what if's" as it is non-productive. Right now I have a palpable lump that is not seen on mammogram. We are thinking it is benign, possibly scar tissue, but I am scheduled for an MRI on Friday, just to be sure. Am I worried? Not really, as I know that most lumps are benign and cancerous ones have certain characteristics which are seen on mammograms.
Usually, a breast specialist can accurately spot the characteristics of a benign tumor vs a cancerous one. However, it is the opinion of the "doctor's doctor" specialist I use for second opinion (so good he does not take insurance), that a core needle biopsy should be done to confirm the diagnosis. Once the diagnosis is confirmed as benign, the tumor still needs to be watched for growth, as it may need to be excised if it gets too large. Most get smaller over time (except 80% of mine, LOL).
So visit the specialist and don't get stressed out. It is probably benign. If it isn't, then empower yourself with information and the knowlege that you have found it early due to your diligence.