title: Interlaboratory comparison in HercepTest assessment of HER2 protein status in invasive breast carcinoma fixed with various formalin-based fixatives.
abstract: Although formalin-based fixatives are used in pathologic laboratories, there is no strictly standardized fixation protocol in Japan. To examine interlaboratory variation caused by different conditions of fixation in the assessment of human epidermal growth factor receptor (HER) 2 status on pathologic tissues, 274 archival invasive breast carcinomas from 5 different laboratories were evaluated using the HercepTest. In 1 laboratory in which 10% neutral buffered formalin was used, as recommended by the manufacturer, the overexpression rate was 22.4% and fell within the statistical expected range (20%-30%) for HER2 overexpression in breast carcinomas. The overexpression rates in the other 4 laboratories, in which either 20% nonbuffered formalin or 15% neutral buffered formalin was used, were near the expected range for HER2 overexpression. To clarify the influence of prolonged formalin fixation on the HercepTest, we compared 1-day with 7-day fixations using 36 cases fixed with 20% nonbuffered formalin. Of the 36 cases, 7 showed 3+ staining with 1-day fixation and sustained the same scoring results with 7-day fixation, although the staining intensities in these cases were reduced with the prolonged fixation. These results indicated that the immunohistochemical assessment of HER2 status with the HercepTest was comparatively resistant to prolonged fixation conditions and provided stable staining results in positive cases, particularly 3+ patients.
authors.affiliation: Department of Biomedical Science, DakoCytomation Co. Ltd., Kakkyoyama 18, Nishinotoin-higashiiru, Shijo-dori, Shimogyo, Kyoto 600-8493, Japan. kaoru.hashizume@dakocytomation.jp
authors.forename: Kaoru
authors.initials: K
authors.lastname: Hashizume
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hatanaka
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kamihara
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kato
authors.forename: Sakae
authors.initials: S
authors.lastname: Hata
authors.forename: Shizuka
authors.initials: S
authors.lastname: Akashi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Kato
authors.forename: Junichi
authors.initials: J
authors.lastname: Koyatsu
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Tani
authors.forename: Masahiko
authors.initials: M
authors.lastname: Tsujimoto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tsuda
mesh_terms: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis*; D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology*; D005260:Female; D005557:Formaldehyde; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D015588:Observer Variation; D011933:Reagent Kits, Diagnostic / Q000592:standards; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D005557:Formaldehyde; D011933:Reagent Kits, Diagnostic; D018719:Erb-b2 Receptor Tyrosine Kinases