HER2 ISH Dual Probe Copy Number
**Note 1:** Physician statement of HER2 in situ hybridization (ISH) Dual Probe Copy Number can be used to code this data item.
**Note 2:** A dual probe test will report average number or mean signals per cell for both HER2 and CEP17, the latter used as a control. Record the HER2 average number or mean signals per cells in this data item. The average number or mean signals per cells is also called the copy number.
SISH RESULTS: FINAL HER2 IN SITU HYBRIDIZATION INTERPRETATION: EQUIVOCAL, INDETERMINATE. HER2 gene copy between 4 & 6 with HER2/CEP17 ratio <2.
HER2/CEP17 RATIO: 4.26 / 3.13 = 1.36
HER-2/neu SILVER IN SITU HYBRIDIZATION (SISH)
HER-2neu gene (Inform HER2 DNA probe)
Number of tumor cell nuclei counted: 120
Number of Her-2/neu gene copies: 511
Mean HER-2/neu gene copy number: 4.26
CEP-17 SILVER IN SITU HYBRIDIZATION (SISH)
CEP-17 (Inform Chromosome 17 probe)
Number of cell nuclei counted: 60
Number of CEP-17 gene copies: 188
Mean CEP-17 gene copies/nucl: 3.13
Code Dual Probe HER2 Copy Number: 4.2
[Note: This is calculated by dividing 511 by 120]
**Note 3:** **Registrars are not to calculate the copy number.**
**Note 4:** Following ASCO-CAP guidelines, a 2+ (equivocal) finding by **immunohistochemistry (IHC)** should result in additional testing with ISH to determine gene copy number.
**Note 5:** Any type of ISH test (e.g., FISH, CISH, SISH) can be used to code this data item. The same test should be used to code all the HER2 ISH data items.
**Note 6:** A HER2 ISH test may be called “ERBB2.” ERBB2 is the standard symbol for the gene ‘erb-b2 receptor tyrosine kinase 2.’ An IHC test identifies the protein expressed by the gene, and an ISH test identifies the gene itself.
**Note 7:** If a HER2 ISH single probe copy number test is done, and the results are between 4 and 6 (equivocal), dual probe tests are recommended.
**Note 8:** If the test results are presented to the hundredth decimal, ignore the hundredth decimal. Do NOT round.
Reported as 4.99, code as 4.9