Ductal Epithelial Lesions: Ductal Carcinoma In Situ vs Atypical Ductal Hyperplasia vs Flat Epithelial Atypia

Before the era of mammography, ductal carcinoma in situ (DCIS) comprised only less than 3% of newly diagnosed breast cancers, most as large palpable masses, and many with microscopic foci of invasion. With widespread use of mammography, DCIS now makes up about 25% of breast cancers diagnosed in the U.S., most as non-palpable lesions. There is also concurrent increased prevalence of atypical ductal hyperplasia (ADH) and flat epithelial atypia (FEA): ADH increases from 2% in premammographic biopsies up to 12% in mammographically screened women; while FEA (which was designated under various names) was rare and not recognized by many pathologists in premammographic biopsies, it is now being diagnosed in about 3.6% of the biopsies performed for microcalcifications.