[160] HER2/neu Testing in Breast Carcinoma. Concordance Study Fluorescent In Situ Hybridization (FISH) vs. Chromogenic In Situ Hybridization (CISH)

L Elavathil, B Dhesy, J Wiernikowski, D Browning, N Akhtar-Danesh, W Hanna. McMaster University, Hamilton, ON, Canada; Juravinski Cancer Centre, Hamilton, ON, Canada; Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada

Background: HER2/neu testing for breast cancer is primarily done in laboratories using two methodologies, i.e. immunohistochemistry (IHC) for identifying HER2/neu receptor protein over expression and fluorescent in situ hybridization (FISH) for HER2/neu gene amplification. With the recent development in technology, HER2/neu gene amplification can be detected by chromogenic in situ hybridization (CISH). FISH technology requires a fluorescence microscope and special skills and hence cannot be performed by many labs. CISH test slides can be scored using an ordinary light microscope and there is no loss of signals over a long period of time. Both of these are advantages over FISH. The objective of our study was to determine the concordance between FISH versus CISH HER2/neu testing in breast carcinoma.
Design: Fifty cases of invasive breast carcinoma from excisional biopsy specimens with known HER2/neu status by immunohistochemistry were identified from the pathology database. The IHC test scores (using DAKO A0485 antibody) of study group were as follows: 0 (24 cases), 1+ (4 cases), 2+ (9 cases), and 3+ (13 cases). HER2/neu gene amplification was determined by FISH (Vysis Pathvision) and by CISH (ZYMED Inc.). The FISH results were assessed as following: If HER2/CEP17 ratios > 2.2 amplified; <1.8 not amplified; and 1.8-2.2 equivocal. For CISH, the number of HER2 signals per nucleus were counted within 60 nuclei of invasive carcinoma cells, with <6 signals defined as not amplified and 6 signals as amplified. The scoring of CISH results was done by one investigator with no prior knowledge of FISH results. The FISH results were assessed by another investigator with no prior knowledge of CISH results.
Results: This study showed that 49/50 (98%) cases were concordant for FISH and CISH. 1/50 case was discordant (table 1). In this case, no signals were observed (tissue not optimal) by FISH but was negative by CISH.

Table 1

	CISH	FISH	Comment
Amplified	15	15	100% concordant
Not Amplified	35	34	1 case discordant*

*One case no signals were seen by FISH


Conclusions: These results indicate that CISH can be used as an alternative method of testing for HER2/neu gene amplification.
Category: Breast

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 44, Tuesday Morning