What Does A Painful Lump In The Left Breast Indicate?

I felt a lump in my left breast about two weeks after my period. Both breasts are tender, feel pain off and on, and also feel tingling pain - moreso in my left breast. Dr. sent me for mamo and bilateral u/s and the dx on the order is fibroadenosis. I was staring at the screen during the u/s and I don't think the tech was able to visualize w/ the u/s machine - even though she asked me to point out the area, and she felt the lump. She only took snapshots labeling the exact location of the snapshot on the breast. Why wouldn't the lump show up in the u/s? (I'm assuming because she didn't mark anything and kept asking if it was the right spot.) I'm 41 and haven't gone through menopause. The report isn't available yet.