Breast Flat Ductal Epithelial Atypia

**Semantic type:** Neoplastic Process

**Definition:** A breast lesion characterized by the presence of dilated terminal ductal lobular units in which the epithelial lining has been replaced by a single layer of mildly atypical cells, or there is atypical, monotonous epithelial hyperplasia of three to five layers. This lesion relates to columnar cell change with atypia and columnar cell hyperplasia with atypia.

**Synonyms:** - Clinging Carcinoma - Clinging Carcinoma In Situ - DIN 1A - Ductal Intraepithelial Neoplasia, Grade 1A - FEA - Flat Ductal Epithelial Atypia - Flat Ductal Epithelial Atypia of the Breast - Flat Epithelial Atypia - Flat Epithelial Atypia of the Breast