Korean J Pathol.  2011 Dec;45(6):665-669.

HER2-Positive Breast Carcinomas with Co-amplification or Gain of Chromosome 17 Centromere Locus: Report of Three Cases and an Impact on HER2 Testing

• Shin HC
• Bae YK
• Kim A
• Park SJ

Abstract

Recently we experienced three cases of human epidermal growth factor receptor 2 (HER2)-amplified invasive breast carcinomas associated with co-amplification or gain of chromosome 17 centromere (CEP17) in silver-enhanced in situ hybridization (SISH) analysis. These cases revealed 2+ or 3+ staining for HER2 immunohistochemistry and >6 HER2 copies per cell on SISH analyses. However, the calculated HER2/CEP17 ratios were low (<2.2) and did not fit within the HER2-positive category. We interpreted those cases as HER2-positive tumors based on the number of HER2 copies per cell. There is a potential for misinterpretation of SISH analysis in cases showing increased CEP17 copy number, based on the criterion used for HER2 positivity (HER2 copies >6 per cell vs HER2/CEP17 ratio>2.2). We recommend reporting raw SISH or fluorescence in situ hybridization data, including number of cells counted, average numbers of HER2 and CEP17 signals, and the calculated HER2/CEP17 ratio to prevent underreporting of HER2 amplification.

Keyword

Breast neoplasms; HER2; Amplification; Chromosome 17; Polysomy

MeSH Terms

Breast
Breast Neoplasms
Centromere
Chromosomes, Human, Pair 17
Coat Protein Complex I
Fluorescence
Humans
Immunohistochemistry
In Situ Hybridization
Receptor, Epidermal Growth Factor
Receptor, erbB-2
Coat Protein Complex I
Receptor, Epidermal Growth Factor
Receptor, erbB-2