Effects of the Change in Cutoff Values for Human Epidermal Growth Factor Receptor 2 Status by Immunohistochemistry and Fluorescence In Situ Hybridization: A Study Comparing Conventional Brightfield Microscopy, Image Analysis-Assisted Microscopy, and Interobserver Variation

Abstract

N Context.-New guidelines for HER2 testing have been introduced.Objectives.-To evaluate the difference in HER2 assessment after introduction of new cutoff levels for both immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) and to compare interobserver agreement and time to score between image analysis and conventional microscopy.Design.-Samples from 150 patients with breast cancer were scored by 7 pathologists using conventional microscopy, with a cutoff of both 10% and 30% IHC-stained cells, and using automated microscopy with image analysis. The IHC results were compared individually and to HER2 status as determined by FISH, using both the approved cutoff of 2.0 and the recently introduced cutoff of 2.2.Results.-High concordance was found in IHC scoring among the 7 pathologists. The 30% cutoff led to slightly fewer positive IHC observations. Introduction of a FISH equivocal zone affected 4% of the FISH scores. If cutoff for FISH is kept at 2.0, no difference in patient selection is found between the 10% and the 30% IHC cutoff. Among the 150 breast cancer samples, the new 30% IHC and 2.2 FISH cutoff levels resulted in one case without a firm diagnosis because both IHC and FISH were equivocal.

Investigating Various Thresholds as Immunohistochemistry Cutoffs for Observer Agreement

“…This number is comparable to the IHC biomarker and histopathology literature (4 to 7 participants) where observer agreement was investigated 44,[55][56][57] . In addition, the participants in the current study were practising pathologists with variable levels of experience as compared to studies where either physicians (with no formal pathology experience) 44 or researchers with experience in IHC were recruited 56 .…”

A Retrospective Population-Based Comparison of HER2 Immunohistochemistry and Fluorescence In Situ Hybridization in Breast Carcinomas: Impact of 2007 American Society of Clinical Oncology/ College of American Pathologists Criteria

“…In support of this, we observed a significant (4.2%) reduction in FISH-positive cases after 2007 as previously communicated. 9,14 As expected by the use of more stringent criteria for IHC positivity, a mild (1.6%, nonstatistically significant) reduction in IHC-positive cases and a significant 8.1% increase in IHC equivocal cases was also found after 2007 (Tables 4 and 5).…”

“…4,[8][9][10] Appropriate positive and negative controls were used for each run. Specimens were fixed in 10% buffered formalin for 2 to 24 hours.…”

“…The impact of the changed interpretation criteria has been a matter of recent interest and controversy. [7][8][9] At Yale School of Medicine, New Haven, Connecticut, a decision was made in 2002 to do both IHC and FISH on every case. Recently, the data have been retrieved into a secondary database to allow retrospective assessment of the assays in a routine clinical basis at a tertiary care center.…”

The Value of Thioredoxin Family Proteins and Proliferation Markers in Dysplastic and Malignant Gallbladders in Patients with Primary Sclerosing Cholangitis

“…The proportion of positive cells divided into two categories: negative \30% and positive C30%. The cut off level of 30% was based on previous studies in order not to overestimate the number of positive cells [25,26].…”