Pre-Invasive Lesions of the Breast: WHO Update Atypical Ductal Hyperplasia Flat Epithelial Atypia Stuart J. Schnitt, M.D. Department of Pathology Beth...
Pre-Invasive Lesions of the Breast: WHO Update Atypical Ductal Hyperplasia Flat Epithelial Atypia Stuart J. Schnitt, M.D. Department of Pathology Beth Israel Deaconess Medical Center and Harvard Medical School Boston, MA, USA
Immunophenotype of UDH • Mixed population of cells that express low and high molecular weight cytokeratins (the latter often in a heterogeneous or mosaic pattern)
HMW-CK in UDH CK 5/6
UDH: “Triple Stain” LMW-CK red, HMW-CK brown cytop, Myoep cells brown nuclear
Immunophenotype of UDH • Mixed population of cells that express low and high molecular weight cytokeratins (the latter often in a heterogeneous or mosaic pattern) • Heterogeneous expression of ER
ER in UDH
Atypical Ductal Hyperplasia • Defined in terms of its resemblance to low grade DCIS • Diagnosis of ADH should not be made unless a diagnosis of low grade DCIS is being seriously considered • Florid examples of usual ductal hyperplasia (UDH) should not be categorized as ADH • If there is uncertainty as to whether to categorize a lesion as UDH or ADH, categorize it as UDH
Morphological Criteria for ADH WHO, 2012
LG-DCIS
LG-DCIS
ADH
Immunophenotype of ADH • Uniform population of cells that lack expression of high molecular weight cytokeratins
HMW-CK in Atypical Ductal Hyperplasia CK 5/6
Immunophenotype of ADH • Uniform population of cells that lack expression of high molecular weight cytokeratins • Strong, diffuse expression of ER
Extent Criteria to Distinguish ADH from Low Grade DCIS • Lesions that show partial involvement of spaces by cells similar to those of LG-DCIS are given the diagnosis of ADH
Extent Criteria to Distinguish ADH from Low Grade DCIS • Lesions that possess ALL of the qualitative features of LG-DCIS but are limited in extent are given the diagnosis of ADH: –1985, Page et al:
