Digital image analysis improves the quality of subjective HER-2 expression scoring in breast cancer

Aim: To compare HER-2 scoring reproducibility by subjective and digital image analysis (DIA) scores with each other and with fluorescence in situ hybridization (FISH) assessed HER-2 amplification. Methods: Herceptest-stained Tissue Micro Arrays of 219 breast carcinomas were scored (DAKO protocol) by 3 observers (both independent and as consensus), scored by DIA and both scores were compared with FISH amplification results. Results: Interobserver subjective scores reproducibility was good (kappa 0.82 to 0.86) but therapeutically important 3 + /2 + discrepancies occurred in 11% to 16% of all 3 + cases. Subjective scores and FISH results differed considerably, Consensus scores by 3 pathologists correlated better with FISH, reducing the number of both Immunohistochemical (IHC) negative/FISH positives and IHC 3+/FISH negatives. DIA scores were well reproducible and correlated better with FISH amplification than did subjective scores. Conclusions: DIA scores were comparable with consensus scores between 3 expert pathologists, were very well reproducible and performed better in classifying IHC 3+/FISH+ cases than did subjective scores.