Borderline HER-2 breast cancer cases: histochemical versus real-time PCR analysis and impact of different cut-off values.
Seventy-one cases that had resulted borderline for HER-2 protein expression at conventional immunohistochemical assay (2+) were assessed for HER-2 gene amplification by real-time PCR and by FISH in accordance with the manufacturer's recommendations (gene amplification with ratio >or=2 in both methods). Thirty-three out of 71 cases (47%) resulted amplified at real-time PCR analysis, whereas 15 cases resulted positive at FISH (21%). Apparently, PCR was more sensitive than FISH in HER-2 determination, only 10 cases resulting amplified in both tests. When the mean ratio value obtained in all PCR experiments was adopted as threshold in determining HER-2 gene amplification, the apparent sensitivity of PCR was reduced but correlation between PCR and FISH results was dramatically increased. Furthermore, when the mean PCR ratio value observed in the FISH-positive group was chosen as threshold, the best agreement between PCR and FISH results was achieved. Therefore, we found that the proposed threshold ratio value of >or=2 is not accurate in separating HER-2 amplified and non-amplified cases. We suggest that the threshold ratio value in PCR tests should be determined in each laboratory using FISH controlled cases. Finally, above certain in-lab generated threshold values, PCR might be proposed as a highly predictive positive test in HER-2 assessment.
Monego
G
G
Institute of Anatomy and Cellular Biology, Faculty of Medicine Agostino Gemelli, Catholic University of Sacred Heart, Rome, Italy.
Arena
V
V
Maggiano
N
N
Costarelli
L
L
Crescenzi
A
A
Zelano
G
G
Amini
M
M
Capelli
A
A
Carbone
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005260:Female; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008875:Middle Aged; D016612:Paraffin Embedding; D011237:Predictive Value of Tests; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity
D018719:Erb-b2 Receptor Tyrosine Kinases