Survivor since 2003
That is good that you will be having a mammogram on Monday since the doctor found a lump you will probably have diagnostic mammograms which they do additional views so a little more films taken a little more squeezing they will probably try to zoom in to the area with the lump. They may also do an ultrasound of the area.
Remember A lump maybe many things a cyst, friboadenoma (a benign growth).
Focus on the positive that you are getting it checked out and your doctor is not sitting on it with the wait and see attitude. Sounds like you are in good hands.
Take care sending positive vibes your way