Clinicopathologic characteristics of HER2 FISH-ambiguous breast cancer at a single institution.

Abstract

BACKGROUND:

: The typical algorithm for human epidermal growth factor-2 (HER2) testing is immunohistochemistry (IHC), followed by reflex HER2 fluorescence in situ hybridization (FISH) for HER2 IHC-ambiguous (2+) cases. At our institution, HER2 FISH testing is initially performed as part of routine breast cancer testing, with HER2 FISH-ambiguous (HER2:CEP17 ratio, 1.8 to 2.2) cases reflexed to HER2 IHC. This provides a unique dataset for lesions that may not routinely undergo FISH testing. The clinicopathologic characteristics of HER2 FISH-ambiguous cases are described.

DESIGN:

: The electronic pathology database in our institution was searched for HER2 FISH-ambiguous cases from 2007 to December 2011. Review of clinical and pathologic characteristics was performed.

RESULTS:

: Sixty cases from 60 patients were reported as HER2 FISH ambiguous. Reflex HER2 IHC testing was performed on all 60 cases, of which 26 were HER2 IHC negative (0 to 1+), 18 were HER2 IHC ambiguous (2+), and 16 were HER2 IHC positive (3+). Of the 46 HER2 FISH-ambiguous patients with available clinical records, 13 (32%) pursued anti-HER2 treatment (10 IHC 3+, 1 IHC 2+, 2 IHC 0 to 1+). All were grade II or III ductal carcinomas, with 1 grade III metaplastic carcinoma.

CONCLUSIONS:

: Reflex HER2 IHC testing after initially ambiguous HER2 FISH testing provides definitive HER2 status in a majority of cases (70%). However, a substantial percentage (30%) of HER2 FISH-ambiguous cases is also HER2 IHC ambiguous, suggesting an intermediate HER2 biology. Most HER2 FISH-ambiguous patients who received trastuzumab were HER2 IHC 3+, grade III, and had associated high-grade ductal carcinoma in situ. Although not statistically significant and with only minimal follow-up, no recurrences have occurred in those patients treated with trastuzumab (P=0.5754).

• Authors: Michael R Clay, David J Iberri, Charles D Bangs, Athena Cherry, Kristin C Jensen
• Journal: The American journal of surgical pathology (Am J Surg Pathol) Vol. 37 Issue 1 Pg. 120-7 (Jan 2013) ISSN: 1532-0979 [Electronic] United States
• PMID: 23108020 (Publication Type: Journal Article)

Chemical References

• Antibodies, Monoclonal, Humanized
• Antineoplastic Agents
• Biomarkers, Tumor
• ERBB2 protein, human
• Receptor, ErbB-2
• Trastuzumab

Topics

• Adult
• Aged
• Aged, 80 and over
• Antibodies, Monoclonal, Humanized (therapeutic use)
• Antineoplastic Agents (therapeutic use)
• Biomarkers, Tumor (genetics, metabolism)
• Breast Neoplasms (diagnosis, drug therapy, genetics)
• Carcinoma, Ductal, Breast (diagnosis, drug therapy, genetics)
• Carcinoma, Intraductal, Noninfiltrating (diagnosis, drug therapy, genetics)
• Combined Modality Therapy
• Databases, Factual
• Female
• Humans
• Immunohistochemistry (methods)
• In Situ Hybridization, Fluorescence
• Mastectomy
• Middle Aged
• Neoplasm Recurrence, Local
• Neoplasm Staging
• Receptor, ErbB-2 (genetics, metabolism)
• Reproducibility of Results
• Trastuzumab
• Young Adult