[141] Evaluation of HER2 IHC Staining Using the Ventana Image Analysis System, Correlation with HER2 FISH Amplification

Jake A Dennis, Rezvaneh Parsa, Donnie Chau, Yan Peng, Sunati Sahoo, Yisheng V Fang, Venetia R Sarode. UT Southwestern, Dallas, TX

Background: Overexpression of HER2 is seen in 15 to 20% of invasive breast carcinoma. HER2 positivity by IHC is graded as 0, 1+, 2+, and 3+ based on the extent and intensity of cytoplasmic membrane positivity. HER2 FISH is considered the gold standard for IHC positivity. Concordance between HER2 IHC positivity and FISH amplification is between 80 to 95%. The Ventana Image Analysis System (VIAS) is a computer-based method of IHC scoring that provides continuous values. The positive score generated by the VIAS algorithm ranges from 2.5 to 3.5. However, adjusting the manufacturer's positive cut-off values may allow for increased specificity for HER2 amplification by FISH.
Design: 533 cases with IHC staining and FISH analysis for HER2 were retrospectively analyzed. Tumor sections were stained with Ventana PATHWAY© anti-HER-2/neu (4B5) antibody using automated method. Image analysis was performed using the VIAS platform according to the manufacturer's specifications. The manufacturer's cutoff scores for 0, 1+, 2+, and 3+ are 0-0.5, 0.51-1.5, 1.51-2.5, and 2.51-3.5 respectively. FISH analysis was performed using the PathVysion Kit. HER2 amplification was defined as a HER2/CEP17 ratio of >2.2, borderline amplification was 1.8 to 2.2 and negative was <1.8. In our laboratory, the positive threshold for the 3+ IHC was increased from 2.51 to 3.5 and those below 3.5 were interpreted as 2+. Sensitivity and specificity for HER2 positivity at the two levels were compared with FISH results.
Results: Raising the IHC cut-off score for the 3+ category from 2.51 to 3.5 moved 52 out of 533 cases from the positive to intermediate (2+) IHC category. Of these, 28 were HER2 negative by FISH, 23 were HER2 positive, and 1 had borderline amplification. This increased the specificity from 91.3% to 99.2% and lowered the false positive rate from 5.8% to 0.6%.

Table 1
VIAS ScoreNON AMPAmpBorderlineMean ScoreStd Dev
0 (0-0.5) n = 9289 (96.7%)1 (1.1%)2 (2.2%)0.2160.146
1+ (0.51-1.5) n = 8175 (92.6%)4 (4.9%)2 (2.5%)1.0030.289
2+ (1.51-3.49) n = 231188 (81.4%)39 (16.9%)4 (1.7%)2.1500.513
3+ (3.5+) n = 1293 (2.3%)124 (96.1%)2 (1.6%)3.5000



Conclusions: The VIAS is a valuable tool for assessing HER2 overexpression in breast carcinoma. However, the manufacturer's IHC cutoff for HER2 positivity resulted in a false positive rate of 5.8%. Raising the 3+ cutoff value from 2.51 to 3.5 decreased the false positive rate to 0.6% and increased specificity to 99.2%. FISH testing should be performed for VIAS IHC scores of 1.51 to 3.49.
Category: Breast

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 19, Monday Morning

 

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