HER2 IHC Summary
**Note 1:** Physician statement of HER2 IHC Summary can be used to code this data item when no other information is available.
**Note 2:** The HER2 IHC test performed on the primary breast tissue is to be recorded in this data item.
**Note 3:** Results from nodal or metastatic tissue may be used, ONLY when there is no evidence of primary tumor.
**Note 4:** In cases where HER2 IHC is reported on more than one breast tumor specimen, record the highest value. If any sample is positive, record as positive.
**Note 5:** If neoadjuvant therapy is given, record the assay from tumor specimens prior to neoadjuvant therapy.
* If neoadjuvant therapy is given and there are no HER2 IHC results from pre-treatment specimens, report the findings from post-treatment specimens.
**Note 6:** If HER2 IHC is positive on an in situ specimen and HER2 IHC is negative on all tested invasive specimens, code HER2 IHC as negative (code 0).
**Note 7:** A 2+ (equivocal) finding by IHC should result in additional testing with ISH to determine gene copy number.
**Note 8:** An immunohistochemistry (IHC) test identifies the protein expressed by the gene (ERBB2), and an in situ hybridization (ISH) test identifies the number of copies of the gene (ERBB2) itself.