title: Bright-field HER2 dual in situ hybridization (DISH) assay on breast cancer cell blocks: a comparative study with histological sections.
abstract: BACKGROUND
  HER2 testing for samples from recurrent or metastatic disease is recommended by the 2013 update of the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines and cytological analysis can be applied to several types of metastatic lesions. However, the practical method to assess the HER2 testing of breast cancer cytology specimens has yet to be resolved. Therefore, we conducted the bright-field HER2 dual in situ hybridization (DISH) assay on cell blocks (CBs) prepared from breast cancer cell samples as a validation study before clinical use.
  
  
  METHODS
  CBs were prepared from tumor cell samples collected from 54 surgically excised breast tumors. The cells were fixed in 10 % buffered formalin for 16-28 h, and embedded in paraffin. The INFORM HER2/neu Dual ISH DNA Probe Cocktail was used for the DISH assay on the Ventana BenchMark ULTRA (Roche Diagnostics).
  
  
  RESULTS
  Successful results were obtained in 51 of 54 CB specimens, and the results from the CB specimens were in agreement with those from the histological sections in 48 of the 51 cases (concordance rate, 94 %; kappa, 0.846). The intraclass correlation coefficient (ICC) between the CB and histological specimens in the continuous HER2/CEP17 signal count ratio was 0.89 (95 % CI 0.81-0.93), and the Pearson's CC was 0.91 (95 % CI 0.85-0.94).
  
  
  CONCLUSIONS
  The HER2 DISH assay, utilizing 10 % buffered formalin-fixed CB, would be a reliable and ideal method to assess the HER2 gene status of breast cancer cytological specimens.
authors.affiliation: Department of Clinical Laboratory, National Hospital Organization Shikoku Cancer Center, 160 Kou, Minamiumemoto-machi, Matsuyama, Ehime, 791-0280, Japan. rnishimu@shikoku-cc.go.jp.
authors.forename: Rieko
authors.initials: R
authors.lastname: Nishimura
authors.affiliation: Department of Clinical Laboratory, National Hospital Organization Shikoku Cancer Center, 160 Kou, Minamiumemoto-machi, Matsuyama, Ehime, 791-0280, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Okamoto
authors.affiliation: Department of Clinical Laboratory, National Hospital Organization Shikoku Cancer Center, 160 Kou, Minamiumemoto-machi, Matsuyama, Ehime, 791-0280, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Satou
authors.affiliation: Department of Clinical Laboratory, National Hospital Organization Shikoku Cancer Center, 160 Kou, Minamiumemoto-machi, Matsuyama, Ehime, 791-0280, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Kojima
authors.affiliation: Department of Clinical Laboratory, National Hospital Organization Shikoku Cancer Center, 160 Kou, Minamiumemoto-machi, Matsuyama, Ehime, 791-0280, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Division of Clinical Biostatistics, Section of Cancer Prevention and Epidemiology, Clinical Research Center, National Hospital Organization Shikoku Cancer Center, Matsuyama, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Yamashita
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D013048:Specimen Handling / Q000379:methods
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: Breast cancer; Cell block; Cytology; DISH; HER2 gene