title: Bimodal frequency distribution of estrogen receptor immunohistochemical staining results in breast cancer: an analysis of 825 cases.
abstract: Immunohistochemical analysis is used routinely to determine the estrogen receptor (ER) status of breast cancers in paraffin sections. However, lack of standardization has raised concerns that weakly ER+ tumors often are classified erroneously as ER-. To determine the frequency of weakly ER+ tumors, we reviewed ER immunostains of 825 breast cancers. For each case, we estimated the proportion of ER+ tumor cells and also determined an Allred score (which results in scores of 0 or 2 through 8, based on staining intensity and proportion of positive cells). In 817 cases (99.0%), tumor cells showed complete absence of staining or staining in 70% or more of the cells. Similarly, 818 cases (99.2%) exhibited Allred scores of 0 or of 7 or 8. Thus, with the immunohistochemical method used in our laboratory, ER staining is essentially bimodal. The overwhelming majority of breast cancers are either completely ER- or unambiguously ER+, and cases with weak ER immunostaining are rare.
authors.affiliation: Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Collins
authors.forename: Maria L
authors.initials: ML
authors.lastname: Botero
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Schnitt
mesh_terms: D001943:Breast Neoplasms / Q000737:chemistry*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D011960:Receptors, Estrogen / Q000032:analysis*; D013194:Staining and Labeling
chemical_list: D011960:Receptors, Estrogen