title: An International Ki67 Reproducibility Study in Adrenal Cortical Carcinoma.
abstract: Despite the established role of Ki67 labeling index in prognostic stratification of adrenocortical carcinomas and its recent integration into treatment flow charts, the reproducibility of the assessment method has not been determined. The aim of this study was to investigate interobserver variability among endocrine pathologists using a web-based virtual microscopy approach. Ki67-stained slides of 76 adrenocortical carcinomas were analyzed independently by 14 observers, each according to their method of preference including eyeballing, formal manual counting, and digital image analysis. The interobserver variation was statistically significant (P<0.001) in the absence of any correlation between the various methods. Subsequently, 61 static images were distributed among 15 observers who were instructed to follow a category-based scoring approach. Low levels of interobserver (F=6.99; Fcrit=1.70; P<0.001) as well as intraobserver concordance (n=11; Cohen κ ranging from -0.057 to 0.361) were detected. To improve harmonization of Ki67 analysis, we tested the utility of an open-source Galaxy virtual machine application, namely Automated Selection of Hotspots, in 61 virtual slides. The software-provided Ki67 values were validated by digital image analysis in identical images, displaying a strong correlation of 0.96 (P<0.0001) and dividing the cases into 3 classes (cutoffs of 0%-15%-30% and/or 0%-10%-20%) with significantly different overall survivals (P<0.05). We conclude that current practices in Ki67 scoring assessment vary greatly, and interobserver variation sets particular limitations to its clinical utility, especially around clinically relevant cutoff values. Novel digital microscopy-enabled methods could provide critical aid in reducing variation, increasing reproducibility, and improving reliability in the clinical setting.
authors.affiliation: Departments of *Pathology ∥Bioinformatics ¶¶¶Medical Oncology ∥∥∥Internal Medicine, Division of Endocrinology, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam ††Laboratory for Pathology, PAL Dordrecht, Dordrecht ###Department of Pathology, Reinier de Graaf Hospital, Delft ****Department of Pathology, University Medical Center Utrecht, Princess Maxima Center for Pediatric Oncology, Utrecht, The Netherlands †Department of Histopathology, King's College Hospital, London ***Department of Pathology, University Hospitals Birmingham, Birmingham †††Department of Histopathology, Royal Hallamshire Hospital, Sheffield, UK ‡Department of Clinical and Molecular Medicine, Pathology Unit, Sant' Andrea Hospital, Sapienza University, Rome ¶Department of Oncology, University of Turin at San Luigi Hospital, Orbassano, Italy §Department of Pathology, Department of Internal Medicine, University of Michigan Comprehensive Cancer Center, University of Michigan Health System, Ann Arbor, MI #Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI **Department of Pathology and Laboratory Medicine, Tufts Medical Center, Tufts University School of Medicine ‡‡Department of Pathology, Massachusetts General Hospital, Boston, MA §§Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN ∥∥Department of Pathology, University Health Network, University of Toronto, Toronto, ON, Canada ¶¶Department of Anatomical Pathology, Royal North Shore Hospital and University of Sydney, Sydney, NSW, Australia ##Department of Pathology and Molecular Genetics and Research Laboratory, Hospital Universitari Arnau de Vilanova, IRBLLEIDA, University of Lleida, Lleida, Spain ‡‡‡INSERM U1016 CNRS UMR8104, Institut Cochin, Paris Descartes University, Sorbonne Paris Cité §§§Department of Pathology, Pitié-Salpetrière Hospital, APHP, Pierre and Marie Curie Univers
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Papathomas
authors.forename: Eugenio
authors.initials: E
authors.lastname: Pucci
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Giordano
authors.forename: Hao
authors.initials: H
authors.lastname: Lu
authors.forename: Eleonora
authors.initials: E
authors.lastname: Duregon
authors.forename: Marco
authors.initials: M
authors.lastname: Volante
authors.forename: Mauro
authors.initials: M
authors.lastname: Papotti
authors.forename: Ricardo V
authors.initials: RV
authors.lastname: Lloyd
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Tischler
authors.forename: Francien H
authors.initials: FH
authors.lastname: van Nederveen
authors.forename: Vania
authors.initials: V
authors.lastname: Nose
authors.forename: Lori
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authors.lastname: Erickson
authors.forename: Ozgur
authors.initials: O
authors.lastname: Mete
authors.forename: Sylvia L
authors.initials: SL
authors.lastname: Asa
authors.forename: John
authors.initials: J
authors.lastname: Turchini
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Gill
authors.forename: Xavier
authors.initials: X
authors.lastname: Matias-Guiu
authors.forename: Kassiani
authors.initials: K
authors.lastname: Skordilis
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Stephenson
authors.forename: Frédérique
authors.initials: F
authors.lastname: Tissier
authors.forename: Richard A
authors.initials: RA
authors.lastname: Feelders
authors.forename: Marcel
authors.initials: M
authors.lastname: Smid
authors.forename: Alex
authors.initials: A
authors.lastname: Nigg
authors.forename: Esther
authors.initials: E
authors.lastname: Korpershoek
authors.forename: Peter J
authors.initials: PJ
authors.lastname: van der Spek
authors.forename: Winand N M
authors.initials: WN
authors.lastname: Dinjens
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Stubbs
authors.forename: Ronald R
authors.initials: RR
authors.lastname: de Krijger
mesh_terms: D000293:Adolescent; D000306:Adrenal Cortex Neoplasms / Q000473:pathology*; D018268:Adrenocortical Carcinoma / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D002648:Child; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D019394:Ki-67 Antigen / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010338:Pathology, Clinical / Q000592:standards*; D015203:Reproducibility of Results; D046888:Tissue Array Analysis; D014584:User-Computer Interface; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen