- Flat epithelial atypia is a common subtype of B3 breast lesions and is associated with noninvasive cancer but not with invasive cancer in final excision histology. Noske, A., Pahl, S., Fallenberg, E., Richter-Ehrenstein, C., Buckendahl, A.C., Weichert, W., Schneider, A., Dietel, M., Denkert, C. Hum. Pathol. (2010)