painless thickening left breast

I have thickening on the left breast only, upper middle of breast.  No pain, cannot be moved.  Have it about 12 months.

Prviously, have had no of fluid filled cysts always in left breast, also had biopsy on lump on outer left breast 12 months ago which came back benign.  

I am nearly sure this thickening was there when last mamogram (mammogram) was taken and nothing said.  My doctor now is concerned, is there any need to be??

[CCF-RN,MSN-rf]

Dear kinnity:  Without examination and review of the mammogram films, there is no way for us to speculate on whether this thickening is of concern.  We recommend that you follow your doctor's advice or if you are not comfortable with this approach, consider a second opinion.