title: High-sensitivity epidermal growth factor receptor immunostaining for colorectal carcinomas, compared with EGFR PharmDx™: a study of diagnostic accuracy.
abstract: Immunostaining for epidermal growth factor receptor (EGFR) is important in the contemporary therapeutic strategy of colorectal carcinomas. We tried to increase detection sensitivity, and compared the high-sensitivity EGFR immunostaining with a worldwide standard, EGFR PharmDx™ (Dako). In order to pursue high-sensitivity EGFR detection, deparaffinized sections were pressure-cooked in 1 mM EDTA solution, pH 8.0. Two mouse monoclonal antibodies against EGFR, clone EGFR2.5 and DAK-H1-WT, and six kinds of secondary detection reagents, including biotin-free catalyzed signal amplification (CSA II), Simple Stain MAX-PO, PolyVue, Novolink, EnVision™ FLEX+, and MACH3, were evaluated to compare the results with those with EGFR PharmDx™, employing a combination of 2-18-C9 as the primary monoclonal antibody and EnVision™ as the secondary reagent. Furthermore, we replaced EnVision™ in the EGFR PharmDx™ kit with CSAII. EGFR detection sensitivity was higher with DAK-H1-WT than with EGFR2.5, and among the secondary reagents, the strongest signals were observed with Novolink. All 30 colorectal carcinomas showed distinct expression of EGFR with our high-sensitivity EGFR immunostaining, while only 16 (53%) gave focal positivity with EGFR PharmDx™. When EnVision™ in EGFR PharmDx™ was replaced by CSA II, strong signals were seen in all cases, and the expression pattern was comparable with our sequence. Non-neoplastic crypt epithelial cells often showed weakly signal with the standard EGFR PharmDx™, but consistently revealed strong membrane staining in the two high-sensitivity sequences. EGFR PharmDx™ frequently gave false negativity. Importantly, EGFR was consistently and sensitively detected when the secondary polymer in the EGFR PharmDx™ kit was simply replaced by CSA II.
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine Toyoake, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Shiogama
authors.forename: Trai
authors.initials: T
authors.lastname: Wongsiri
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Mizutani
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Inada
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tsutsumi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D015179:Colorectal Neoplasms / Q000378:metabolism*; D066246:ErbB Receptors / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D051379:Mice; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
chemical_list: D000911:Antibodies, Monoclonal; D011933:Reagent Kits, Diagnostic; C512478:EGFR protein, human; D066246:ErbB Receptors