Comparing Fluorescence In Situ Hybridization and Immunohistochemistry to Determine the HER-2/neu Status in Breast Carcinoma

Park, Kyeongmee; Kim, Jungyoen; Lim, Sungjig

Abstract

BACKGROUND: Identification of HER-2/neu status is important in predicting the response to specific chemotherapy in breast carcinoma patients and HER-2/neu status is associated with poor clinical outcome even with systemic chemotherapy. Introduction of fluorescence in situ hybridization (FISH) allows an accurate assessment of the level of gene amplification with information about distribution of gene copies in histologic sections.
METHODS
HER-2/neu status was performed on paraffin sections of 176 primary breast carcinomas by FISH, using PathVysion and by immunohistochemistry (IHC), using HercepTest. The results of HER-2/neu amplification was compared with clinical and pathological prognostic factors.
RESULTS
HER-2/neu amplification and overexpression were detected in 51 tumors (29.0%) by FISH and 32 tumors (18.2%) by IHC. The results of each method agreed with each other in 157 tumors (concordance: 89.2%, kappa=0.783). HER-2/neu amplification was associated with poor nuclear grade, marked nuclear pleomorphism, and presence of the combined ductal carcinoma in situ in the invasive ductal carcinomas as well as Van Nuys grade of the ductal carcinoma in situ component (p<0.05).
CONCLUSIONS
The comparison of FISH and IHC demonstrated an excellent correlation of HER-2/neu overexpression 2+ and 3+ with gene amplification. However, FISH may be a more accurate and reliable method for negative and 1+ cases. HER-2/neu amplification proves to be of prognostic relevance.