ER CK5/6

Flat epithelial atypia

Columnar cell lesions: A spectrum: columnar cell change, columnar cell

hyperplasia, flat epithelial atypiaFEA 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.

IHC in FEA

Not helpful CCC, CCH, FEA, ADH, low grade DCIS all have the

same immunophenotype ER+, PgR+, HER2 -, E-Cadherin+, LMWK+, HMWK-.