Atypical and typical cells

Hi
Could you please explain to me to the difference in pathophysiology between typical and atypical cells in breast tissue.  Also are there any other types of cells that may be relevant to a lump being benign or malignant?
Thanks in advance

[txgrl01]

A good place for a faily simple explanation is breastcancer.org.  It shows drawings of regular breast cells and those with atypia. I'm faily new to the club but I understand that there are a host of cell changes that can occur, most of them are benign.  Some can lead to a higher risk of cancer down the road.  If you are aking because of pathology report, google the terms you are not sure about.  I found every term on the internet.  Just be careful to read good sites.  There are some sites that just are hawking vitamins, etc.