Analysis of intratumoral heterogeneity and amplification status in breast carcinomas with equivocal (2+) HER-2 immunostaining

Jason T. Lewis, Rhett P. Ketterling, Kevin C. Halling, Carol Reynolds, Robert B. Jenkins, Daniel W. Visscher

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Fluorescence in situ hybridization (FISH) and immunohistochemical analysis for assessment of HER-2 status in breast carcinomas are discordant in a significant proportion of cases with equivocal (2+) immunostaining. To evaluate the role of intratumoral heterogeneity and degree of amplification, we performed additional HER-2 immunostains and FISH on tumor-bearing blocks from 20 invasive breast carcinomas with immunohistochemical scores of 2+ with gene amplification and in 18 cases without amplification. Of the amplified cases, 11 (55%) had a 3+ immunohistochemical score on at least 1 additional slide, 8 (40%) remained 2+, and 1 (5%) had a slide scored 1+. All cases rescored 3+ showed high-level amplification in original and repeated FISH; cases remaining 2+ had a heterogeneous FISH profile (low-level amplification or a mosaic mixture of high-level amplified and nonamplified cells) in original and repeated FISH. Of nonamplified cases, 13 (72%) had a 1+ score on at least 1 additional slide, 4 (22%) remained 2+, and 1 (6%) had 1 slide scored 3+. In the nonamplified cases, 17 (94%) showed no amplification in repeated FISH. Significant intratumoral heterogeneity and minimal (low-level) HER-2 amplification account for many breast cancers with 2+ HER-2 protein expression.

Original languageEnglish (US)
Pages (from-to)273-281
Number of pages9
JournalAmerican journal of clinical pathology
Issue number2
StatePublished - Aug 2005



  • Amplification
  • Breast carcinoma
  • HER-2
  • Immunohistochemistry

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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