Detailed Reanalysis of 500 Breast Cancers with Equivocal HER2 Immunohistochemistry and Borderline ERBB2 Fluorescence in Situ Hybridization Results

Katherine B. Geiersbach, Daniel R. Sill, Kristina M. Del Rosario, Reid G. Meyer, Grant M. Spears, Jason A. Yuhas, William R. Sukov, Robert Brian Jenkins, Idris T. Ocal, Taofic Mounajjed, Beiyun Chen

Research output: Contribution to journalArticlepeer-review

Abstract

Objectives: We investigated the impact of our laboratory's reflex testing process for resolving ERBB2 (HER2) status on breast cancer samples that require additional workup after fluorescence in situ hybridization (FISH), per guideline recommendations published in 2018 by the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP). Methods: In total, 500 breast cancer specimens with ERBB2 FISH results in groups 2 through 4 (all reported as immunohistochemistry [IHC] equivocal [2+] at external laboratories) were resubmitted for IHC testing in our laboratory. Per the ASCO/CAP guideline, FISH was rescored when internal IHC was also equivocal (2+), targeted to tumor areas demonstrating more intense IHC staining, if observed. Results: Reflex IHC/FISH testing changed the final reported ERBB2 status in 185 of 500 (37.0%) samples. Result changes included discordant IHC (n=4 score 0, n=132 score 1+, and n=16 score 3+) and discordant FISH (n=33). Numerical differences in FISH scores were comparable for targeted vs nontargeted FISH rescoring (P=.086 for ERBB2 copy number; P=.49 for ERBB2 ratio). Two cases showed larger differences in FISH scores, suggesting heterogeneity. Conclusions: Retesting of breast cancer samples with equivocal IHC frequently changes IHC results, but targeted reanalysis of borderline FISH results rarely identifies significant differences in ERBB2 copy number or ratio.

Original languageEnglish (US)
Pages (from-to)886-894
Number of pages9
JournalAmerican journal of clinical pathology
Volume156
Issue number5
DOIs
StatePublished - Nov 1 2021

Keywords

  • Breast cancer
  • FISH
  • HER2
  • Image analysis
  • Immunohistochemistry

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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