HER2 Amplification Associated with Breast Cancer, FISH, Tissue
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
HER2 (ERBB2: c-erb-b2) is an oncogene on the long arm of chromosome 17 that is amplified in approximately 15% to 20% of breast cancers. Amplification or overexpression of HER2 has been shown to be associated with shorter disease-free survival and poorer overall survival in both node-negative and node-positive ductal breast cancers. Patients with HER2 gene amplification or overexpression are candidates for treatment with the drugs that target the human epidermal growth factor receptor 2 (HER2) protein or its downstream pathways (eg, trastuzumab [Herceptin], pertuzumab, lapatinib).
FISH with labeled DNA probes to the pericentromeric region of chromosome 17 and to the HER2 locus can be used to determine if a patient's breast cancer has HER2 gene amplification. Immunohistochemical analysis is used to determine if a tumor exhibits HER2 overexpression.
FISH has been shown to be superior to Southern, Northern, and Western blots and immunohistochemical analyses for the determination of HER2 amplification in formalin-fixed, paraffin-embedded material. HER2 amplification as detected with FISH has been shown to be an independent predictor of poor clinical outcome.
As a prognostic indicator for patients with both node-positive or node-negative primary and metastatic breast cancer
To guide therapy, as patients with HER2 amplification may be candidates for therapies that target the human epidermal growth factor receptor 2 (HER2) protein (eg, trastuzumab [Herceptin], pertuzumab, lapatinib)
To confirm the presence of HER2 amplification in cases with 2+ (low level) or 3+ (high level) HER2 overexpression by immunohistochemistry
An interpretive report is provided. Results are interpreted utilizing the 2013 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines.
Specimens with equivocal results require reflex or repeat testing per ASCO/CAP guidelines.
The degree of HER2 amplification varies in tumors. Some exhibit high levels of amplification (HER2:CEP17 ratio >4.0), whereas others exhibit low-level amplification (HER2:CEP17 ratio of 2.2-4.0). It is not currently known if patients with different levels of amplification have the same prognosis and response to therapy.
Reports also interpret the HER2 copy number changes relative to chromosome 17 copy number (aneusomy) or potential structural changes that increase HER2 copy number.
Rare cases may not show HER2 amplification but still have human epidermal growth factor receptor 2 (HER2) protein overexpression demonstrated by immunohistochemistry. The clinical significance of HER2 protein overexpression in the absence of HER2 gene amplification is unclear. However, these patients may have a worse prognosis and be candidates for treatments that target the HER2 protein or its downstream pathways.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is only for primary or metastatic breast tumors.
-For urothelial tumors, order FH2UR / HER2 Amplification Associated with Urothelial Carcinoma, FISH, Tissue.
-For gastroesophageal tumors, order FH2GE / HER2 Amplification Associated with Gastroesophageal Cancer, FISH, Tissue.
-For all other tumor types, order FH2MT / HER2 Amplification, Miscellaneous Tumor, FISH, Tissue.
Optimum fixation should be between 6 and 72 hours in 10% neutral buffered formalin. Other types of fixatives should not be used.
The prognostic information provided by the HER2 status of a patient's tumor should not be interpreted in isolation because other prognostic features (eg, lymph node status, tumor size, estrogen/progesterone receptor status) may be of equal or greater importance in determining the patient's prognosis.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
An interpretive report will be provided.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Wolff AC, Hammond ME, Hicks DG, et al: Recommendations for human epidermal growth factor receptor 2 testing in breast cancer: American Society for Clinical Oncology/College of American Pathologists clinical practice guideline update. J Clin Onc 2013 Nov 1;31(31):3997-4013
2. Perez EA, Roche PC, Jenkins RB, et al: HER2 testing in patients with breast cancer: poor correlation between weak positively by immunohistochemistry and gene amplification by fluorescence in situ hybridization. Mayo Clin Proc 2002 Feb;77(2):148-154
3. Romond EH, Perez EA, Bryant J, et al: Trastuzumab plus adjuvant chemotherapy for operable HER2-positive breast cancer. N Engl J Med 2005 Oct 20;353(16):1673-1684
4. Perez EA, Romond EH, Suman VJ, et al: Four-year follow-up of trastuzumab plus adjuvant chemotherapy for operable human epidermal growth factor receptor 2-positive breast cancer: joint analysis of data from NCCTG N9831 and NSABP B-31. J Clin Oncol 2011 Sep 1;29(25):3366-3373
5. Blumenthal GM, Scher NS, Cortazar P, et al: First FDA approval of dual anti-HER2 regimen: pertuzumab in combination with trastuzumab and docetaxel for HER2-positive metastatic breast cancer. Clin Cancer Res 2013 Sep 15;19(18):4911-4916
6. Robidoux A, Tang G, Rastogi P: Lapatinib as a component of neoadjuvant therapy for HER2-positive operable breast cancer (NSABP protocol B-41): an open-label, randomised phase 3 trial. Lancet Oncol 2013 epub: 2013 Oct 3