HER2 ISH Dual Probe Ratio
**Note 1:** This SSDI is no longer required by any of the standard setters starting with 2021 diagnoses.
* For cases diagnosed 2021+, this SSDI may be left blank
**Note 2:** Physician statement of HER2 in situ hybridization (ISH) Dual Probe Ratio can be used to code this data item.
**Note 3:** A dual probe test will report results for both HER2 and CEP17, the latter used as a control. The HER2/CEP17 ratio will be reported. Record the ratio in this data item.
SISH RESULTS: FINAL HER 2 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
Code Dual Probe Ratio: 1.3
**Note 4:** **Registrars are not to calculate the ratio.**
**Note 5:** Following ASCO-CAP guidelines, a 2+ (equivocal) finding by immunohistochemistry (IHC) should result in additional testing with ISH to determine gene copy number.
**Note 6:** Any type of ISH test (e.g., FISH, CISH, SISH) can be used to code this data item. Code this data item using the same report used to record 3854: HER2 ISH Summary.
**Note 7:** 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 8:** If the test results are presented to the hundredth decimal, ignore the hundredth decimal. Do NOT round.
Reported as 1.99, code as 1.9