4. ERCK5/6

5. Flat epithelial atypia Columnar cell lesions:  A spectrum: columnar cell change, columnar cell hyperplasia, flat epithelial atypia FEA has mild cytologic atypia (similar to ADH,DCIS) but without architectural atypia. May be more than one cell layer thick. Cytology: enlarged nuclei, rounding, crowding, loss of polarity, visible nucleoli, few mitoses.

6. IHC in FEA Not helpful  CCC, CCH, FEA, ADH, low grade DCIS all have the same immunophenotype  ER+, PgR+, HER2 -, E-Cadherin+, LMWK+, HMWK-.