HER2 testing by Micro-array, resolving tough diagnostic questions

Accurate reporting of HER2 (ERBB2) gene copy number status in newly diagnosed breast and gastric cancers is critical for selecting patients predicted to respond to anti-HER2 therapy. In current clinical practice, tumors are evaluated for HER2 positivity by protein-based immunohistochemistry (IHC) and/or chromosome 17-based fluorescence in situ hybridization (FISH). In the majority of cases, these testing modalities provide a clearly actionable “positive” or “negative” answer. However, in an estimated 10- to 20% of breast and gastric cancers, both IHC and FISH tests are reported as “equivocal” providing the clinician with no guidance as to the potential effectiveness of targeted anti-HER2 therapy for the patient.
Array-based comparative genomic hybridization (aCGH) provides an alternative molecular testing method for determining HER2 status in breast cancer and resolution of these tough double equivocal specimens. This DNA-based technology uses fluorescently labeled test and reference DNA probes hybridized to a DNA microarray to produce a high-resolution view of the HER2 amplicon in context of the entirety of chromosome 17. The p arm, q arm, and centromere region are subjectively and objectively visualized by CGH revealing, in many cases, complex chromosome 17 rearrangements such as centromere amplification, p arm loss, and additional amplified loci.
PacificDx is pleased to offer HI-RES HER2 testing by aCGH as a tech-only service to the greater clinical community. Please contact us at 949-812-6944 or info@pacificdx.com for referral information.

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