HER2 Amplification Associated with Breast Cancer, FISH, Tissue
As a prognostic indicator for patients with both node-positive or node-negative breast cancer(1)
To guide therapy, as patients with HER2 amplification may be candidates for Herceptin therapy(1)
To confirm the presence of HER2 amplification in cases with 2+ (low-level) or 3+ (high-level) HER2 overexpression by immunohistochemistry(2,3)
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 20% of breast cancers.(1) 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.(1) Patients with HER2 gene amplification or overexpression appear to respond better to cyclophosphamide/doxorubicin/5-fluorouracil (CAF) chemotherapy than patients whose tumors do not exhibit HER2 amplification or overexpression HER2 amplified patients are candidates for treatment with the drug Herceptin (trastuzumab).(8)
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.(2-4) Immunohistochemical analysis is used to determine if a tumor exhibits HER2 overexpression.(1)
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.(2,3) HER2 amplification as detected with FISH has been shown to be an independent predictor of poor clinical outcome.(5)
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.
An interpretive report is provided. Results are interpreted utilizing the 2007 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines.(6)
Specimens with equivocal results (see Method Description) require repeat FISH analysis per ASCA/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 HER2 protein overexpression demonstrated by immunohistochemistry(2). The clinical significance of HER2 overexpression in the absence of HER2 gene amplification is unclear. However, these patients may have a worse prognosis and be candidates for Herceptin treatment.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The PathVysion HER2 DNA Probe Kit has been optimized for formalin-fixed, paraffin-embedded breast tissue specimens. Optimum fixation should be between 6 and 48 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.
Evaluation of amplification of the HER2 gene by FISH in tumors with weakly positive (2+) immunohistochemical staining was performed. A total of 1,556 breast tumor biopsy specimens were referred to Mayo Medical Laboratories, Rochester, MN, for HER2 testing between August and December 2000. Immunohistochemical (IHC) analysis was performed with use of a diagnostic test for the assessment of HER2 overexpression, the Hercep Test. The IHC stained slides were interpreted and scored on a scale ranging from 0 to 3+ according to Food and Drug Administration-approved guidelines. All specimens scored as 2+ were also routinely evaluated by FISH using a HER-2/neu DNA probe kit (PathVysion). Specimens were determined to be amplified if the ratio of HER2 signals to chromosome 17 centromere (CEP17) signals was higher than 2.0. Thirty-eight percent of the specimens evaluated with the HercepTest were scored 0, 35% were 1+, 14% were 2+, and 13% were 3+. Of the 216 tumor specimens scored as 2+, 26 (12%) had a high level of HER2 gene amplification; 54 (25%) demonstrated duplication of HER2; 4 (2%) deleted HER2, CEP17 or both; and 123 (57%) had no apparent HER-2 anomaly, no apparent CEP17 anomaly, nor apparent single gain (aneusomy) of CEP17. The Mayo laboratory was also the reference HER2 testing center for the Intergroup phase III trial that evaluated the use of Herceptin in the adjuvant setter(8). Recent guidelines from the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP), recommend that all specimens with a 2+ HercepTest result be evaluated by FISH for HER2 gene amplification. The results of both assays should be considered before making a decision to recommend anti-HER2 therapy. (7)
HER2 Evaluation by IHC
Score 0, 1+
Clinical decision not to treat with anti-HER2 therapy
Reflex to HER2 testing by FISH
Clinical decision for treatment with anti-HER2 therapy
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Pegram MD, Pauletti G, Slamon DJ: HER-2/neu as a predictive marker of response to breast cancer therapy. Breast Cancer Res Treat 1998;52:65-77
2. Pauletti G, Godolphin W, Press MF, Slamon DJ: Detection and quantitation of HER-2/neu gene amplification in human breast cancer archival material using fluorescence in situ hybridization. Oncogene 1996;13:63-72
3. Press MF, Hung G, Godolphin W, Slamon DJ: Sensitivity of HER-2/neu antibodies in archival tissue specimens: potential source of error in immunohistochemical studies of oncogene expression. Cancer Res 1994;54:2771-2777
4. Masood S, Bui MM, Yung JF, et al: Reproducibility of LSI HER-2/neu SpectrumOrange and CEP 17 SpectrumGreen dual color deoxyribonucleic acid probe kit. For enumeration of gene amplification in paraffin-embedded specimens: a multicenter clinical validation study. Ann Clin Lab Sci 1998;28:215-223
5. Press MF, Bernstein L, Thomas PA, et al: HER-2/neu gene amplification characterized by fluorescence in situ hybridization: poor prognosis in node-negative breast carcinomas. J Clin Oncol 997;15:2894-2904
6. Wolff AC, Hammond ME, Schwartz JN, et al: American Society of Clinical Oncology/College of American Pathologists Guideline recommendations for human epidermal growth factor receptor 2 testing in breast cancer. Arch Pathol Lab Med. 2007 Jan;131(1):18-43
7. 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
8. 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