Potential for false-positive staining with a rabbit monoclonal antibody to progesterone receptor (SP2) - Findings of the UK National External Quality Assessment Scheme for Immunocytochemistry and FISH highlight the need for correct validation of antibodies on introduction to the laboratory
ABSTRACT This study focused on recent assessment results from the United Kingdom National External Quality Assessment Scheme for Immunocytochemistry and Fluorescence In-Situ Hybridisation breast hormone receptor module in which participants were asked to demonstrate progesterone receptors (PRs). The slides consisted of 3 infiltrating ductal breast carcinomas, previously classified as a high PR expresser, a moderate to low PR expresser, and a negative tumor. During this assessment, 2 commercial rabbit monoclonal antibodies, SP2 (Lab Vision/NeoMarkers, Fremont, CA), and 1E2 (Ventana, Tucson, AZ) were used by 15% of the participants. The SP2 rabbit monoclonal antibody showed false-positive and nonspecific staining on the previously established PR-tumor. This article highlights the necessity for all clinical laboratories to validate immunohistochemical methods and protocols when using newly marketed antibodies such as SP2; use composite tissue blocks with known levels of tumor expression such as a high, mid, and negative expression; and participate in internal and external quality assessment schemes, which can highlight potential technical issues in laboratory methods.
SourceAvailable from: Tadahiko Shien[Show abstract] [Hide abstract]
ABSTRACT: We examined estrogen receptor (ER) mRNA expression and molecular subtypes in stage I-III breast cancers that are progesterone receptor (PR) positive but ER and HER2 negative by immunohistochemistry (IHC) or fluorescent in situ hybridization. The ER, PR, and HER2 status was determined by IHC as part of routine clinical assessment (N = 501). Gene expression profiling was done with the Affymetrix U133A gene chip. We compared expressions of ESR1 and MKI67 mRNA, distribution of molecular subtypes by the PAM50 classifier, the sensitivity to endocrine therapy index, and the DLDA30 chemotherapy response predictor signature among ER/PR-positive (n = 223), ER-positive/PR-negative (n = 73), ER-negative/PR-positive (n = 20), and triple-negative (n = 185) cancers. All patients received neoadjuvant chemotherapy with an anthracycline and taxane and had adjuvant endocrine therapy only if ER or PR > 10 % positive. ESR1 expression was high in 25 % of ER-negative/PR-positive, in 79 % of ER-positive/PR-negative, in 96 % of ER/PR-positive, and in 12 % of triple-negative cancers by IHC. The average MKI67 expression was significantly higher in the ER-negative/PR-positive and triple-negative cohorts. Among the ER-negative/PR-positive patients, 15 % were luminal A, 5 % were Luminal B, and 65 % were basal like. The relapse-free survival rate of ER-negative/PR-positive patients was equivalent to ER-positive cancers and better than the triple-negative cohort. Only 20-25 % of the ER-negative/PR-positive tumors show molecular features of ER-positive cancers. In this rare subset of patients (i) a second RNA-based assessment may help identifying the minority of ESR1 mRNA-positive, luminal-type cancers and (ii) the safest clinical approach may be to consider both adjuvant endocrine and chemotherapy.Breast Cancer Research and Treatment 12/2013; 143(2). DOI:10.1007/s10549-013-2763-z · 4.20 Impact Factor
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ABSTRACT: Standardization of controls, both positive and negative controls, is needed for diagnostic immunohistochemistry (dIHC). The use of IHC-negative controls, irrespective of type, although well established, is not standardized. As such, the relevance and applicability of negative controls continues to challenge both pathologists and laboratory budgets. Despite the clear theoretical notion that appropriate controls serve to demonstrate the sensitivity and specificity of the dIHC test, it remains unclear which types of positive and negative controls are applicable and/or useful in day-to-day clinical practice. There is a perceived need to provide "best practice recommendations" for the use of negative controls. This perception is driven not only by logistics and cost issues, but also by increased pressure for accurate IHC testing, especially when IHC is performed for predictive markers, the number of which is rising as personalized medicine continues to develop. Herein, an international ad hoc expert panel reviews classification of negative controls relevant to clinical practice, proposes standard terminology for negative controls, considers the total evidence of IHC specificity that is available to pathologists, and develops a set of recommendations for the use of negative controls in dIHC based on "fit-for-use" principles.Applied immunohistochemistry & molecular morphology: AIMM / official publication of the Society for Applied Immunohistochemistry 04/2014; 22(4):241-52. DOI:10.1097/PAI.0000000000000069 · 2.06 Impact Factor
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ABSTRACT: The aim of this study was to investigate the congruency of routine clinical predictive biomarker evaluations, including ER, PR and Ki67, through immunocytochemistry (ICC) and immunohistochemistry (IHC) in primary breast cancer. Clinicopathological data on all women diagnosed with primary breast cancer at Karolinska University Hospital in 2011 was collected. A total of 346 patients were included in a retrospective paired comparison of predictive biomarker evaluations on direct smear ICC and IHC. This showed a low congruency between findings with the two methods, especially evident for Ki67 (κ = 0.35-0.42). By suggested adjustments to ICC cutoffs, we managed to improve the inter-rater agreement of Ki67-classification slightly to κ = 0.46. Our findings suggest that routine clinical ICC and IHC evaluations of predictive biomarkers produce discordant results. Consequently, basing therapeutic decisions on cytology with cutoffs defined for IHC induces a risk that patients will receive a suboptimal therapy. However, our analysis shows that local adjustments to biomarker cutoff levels may improve congruency and increase the probability of correct classifications. This article is protected by copyright. All rights reserved.Histopathology 12/2013; 64(7). DOI:10.1111/his.12344 · 3.30 Impact Factor