Clinical Significance: 
Recently established guidelines from the American Society for Clinical Pathology (ASCP), College of American Pathologists (CAP), Association for Molecular Pathology (AMP), and/or the American Society of Clinical Oncology (ASCP) recommend HER2 FISH testing as a reflex to further clarify equivocal (2+) immunohistochemistry (IHC) results and as routine testing in colorectal, gastroesophageal (GEJ), and gastric cancers.

https://www.nccn.org/professionals/physician_gls/pdf/colon.pdf

https://www.nccn.org/professionals/physician_gls/pdf/gastric.pdf

https://www.nccn.org/professionals/physician_gls/pdf/esophageal.pdf

Specimen Requirements and Collection:
Formalin fixed tissue containing a sufficient amount of tumor (generally at least several mm of tumor tissue submitted in the tissue block). 

Methodology:
Fluorescent in-situ hybridization (FISH) dual-probe assay

Forms:
Molecular pathology requisition form

Transport:
Send formalin-fixed, paraffin-embedded (FFPE) tissue and cell block containing tumor at room temperature.  Also acceptable 2-unstained, 4-5 micron positively charged slides with 1 post H&E.  Please include a surgical pathology report

Unacceptable specimen:
Specimens fixed in alternative fixatives or metal fixatives (ex. B-plus).  Decalcified specimens.

Reference Range:
HER2/CEP17 ratio >= 2.0 = PRESENT = POSTIVE
HER2/CEP17 ratio < 2.0 = ABSENT = NEGATIVE

Hoffmann M, Stoss O, Shi D, et al. Assessment of a HER2 scoring system for gastric cancer: Results from a validation study.  Histopathology 2008;52:797-5.80

CPT codes:
88377

Test reported:
Results are reported within 7-10 days