Problems In Determining Her2 Status In Breast Carcinoma.
OBJECTIVE
Human epidermal growth factor receptor 2 (HER2) oncoprotein is overexpressed in 15-25% of breast carcinomas and associated with poor outcome. Assessment of HER2 status accurately is important to select patients who will benefit from targeted therapy.


METHODS
In this study immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were used to determine the HER2 status in 308 breast carcinoma cases of which 129 were consultation. The major problems in determining HER2 status and the reasons of discordant results between methods were discussed.


RESULTS
HER2 expression was (-) in 124, (+) in 29, (++) in 92, (+++) in 63 cases. 25 of 76 cases consulted as (++) were evaluated as (++) and 15 of 35 cases consulted as (+++) were evaluated as (+++). HER2 amplification was found in 88 (28.6%) of 308 cases by FISH. 3 of 124 (-), 1 of 29 (+), 22 of 92 (++), 62 of 63 (+++) cases were amplified by FISH. The relation between HER2 expression and amplification was statistically significant (p<0.001). Centromere 17 (CEN 17) region amplification was noted in 11 cases of which 2 were (+++), 9 were (++). 6 of the 11 cases showed focal low level, 1 of them showed diffuse high level amplification.


CONCLUSIONS
The concordance rate between IHC (+++) cases and FISH was 95.4% for consultation cases, 100% for our cases. The final concordance rate for both case groups was 98.4%. The possible reasons of discrepancy were triple negativity, preanalytical and analytical procedures of consultation cases and trucut samples.
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Emel Ebru
EE
Pala
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Ümit
Ü
Bayol
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Alp
A
Özgüzer
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Ülkü
Ü
Küçük
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Çağlar Yıldız
ÇY
Akdeniz
Clinic of Pathology, İzmir Tepecik Training and Research Hospital, İzmir, Turkey.
Özlem
Ö
Sezer
Breast cancer; erbB genes; fluorescence in situ hybridization