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HER2 by IHC, Breast Cancer

CPT 88360

Test Details

Cancer Type


Technology Used


Turnaround Time

2 - 4 days


The HER-2/neu protein is a product of the HER-2/neu oncogene, and the detection of overexpression of the HER-2/neu protein has been associated in clinical evaluations with a decreased survival time and a decreased time to relapse in patients with breast cancer. This IHC test is indicated for identifying breast cancer patients who are eligible for treatment with Herceptin® (IHC 3+ or IHC 2+/ISH amplified), KADCYLA® (IHC 3+ or IHC 2+/ISH amplified) or ENHERTU® (HER2-low: IHC 1+ or IHC 2+/ISH non-amplified).

Special Instructions

Fixation time and fixative used must be indicated on the test request form. Please direct any questions regarding this test to oncology customer service at 800-345-4363.


Use of fixatives other than 10% neutral-buffered formalin or fixation times less than six hours or more than 48 hours may not yield reliable results.


Immunohistochemistry (IHC)


Modi S, et al. DESTINY-Breast04 Trial Investigators. Trastuzumab Deruxtecan in Previously Treated HER2-Low Advanced Breast Cancer. N Engl J Med. 2022 Jul 7;387(1):9-20. doi: 10.1056/
NEJMoa2203690. Epub 2022 Jun 5. PMID: 35665782.

PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody [package insert]. Tucson, AZ: Roche Ventana; 2022.

Wolff AC, Hammond EH, et al: Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: ASCO/CAP Clinical Practice Guideline Focused Update. J Clin Oncol: 36:2105-2122, July 10, 2018.

Specimen Requirements

Information on collection, storage, and volume


Formalin-fixed, paraffin-embedded (FFPE) tumor


One paraffin block or seven unstained, positively-charged air-dried and unbaked slides cut at 4 to 5 microns. This includes specimen requirements for FISH reflex. 


Paraffin block transport pouch or slide mailer

Storage Instructions


Maintain specimen at room temperature.

Causes for Rejection

Tumor other than breast tumor



Specimen should be fixed in 10% neutral-buffered formalin. Fixation time should be between six and 72 hours according to ASCO/CAP guidelines; however, the package insert indicates optimum fixation time between 18 and 24 hours.