Using Immunohistochemistry to Distinguish Between Usual and Atypical Ductal Hyperplasia of the Breast

The differentiation between benign and atypical proliferations of the breast can be aided by the use of immunohistochemical (IHC) stains.

Panel of immunostains:

(1) cytokeratin 5/6 (in the intraductal proliferative component)

(2) estrogen receptor (ER)

Diagnosis	CK 5/6	ER
ductal hyperplasia	positive	negative or weak
atypical ductal hyperplasia (ADH) or DCIS	negative or weak	strongly positive

Lesions where this panel will give misleading results (Dabbs):

(1) benign columnar cell hyperplasia (ER positive)

(2) atypical aprocrine lesions (may be ER negative and/or CK positive)

(3) basal-like DCIS (ER negative and CK positive)

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