Assessment of Interlaboratory Variation in the Immunohistochemical Determination of Estrogen Receptor Status Using a Breast Cancer Tissue Microarray

Abstract

The determination of tumor cell estrogen receptor (ER) expression status by immunohistochemical analysis has become standard practice, yet assay reproducibility has not been assessed adequately. By using a breast cancer tissue microarray, we examined interlaboratory variability in ER reporting. A 2-fold redundant tissue microarray block was created from 29 breast cancers. Unstained slides were distributed to 5 laboratories, and each laboratory immunostained and scored 1 slide for ER. Interlaboratory agreement ranged from moderate to high (overall kappa = 0.54 for 0-3+ grading; overall kappa = 0.84 for negative vs positive assessment of ER status). When 1 observer scored each of the 5 slides, interlaboratory agreement was slightly better (kappa = 0.63 for 0-3+ scoring; kappa = 0.96 for negative vs positive scoring). One laboratory, which had used an antibody and antigen retrieval method different from the others, demonstrated only fair concordance with the other 4 laboratories, but there was substantial intralaboratory interobserver agreement and excellent agreement with an outside observer reviewing the slide stained in that laboratory. The tissue microarray was an efficient and effective tool for identifying variability in ER reporting and should prove valuable in other external quality assurance programs.

The presence of stromal mast cells identifies a subset of invasive breast cancers with a favorable prognosis

“…The H &E stained slides from each case were reviewed and the tumors graded independently according to the Nottingham modification of the Scarth Bloom Richardson method 8 by two pathologists (SD and MH). A representative sample of the invasive component of each breast carcinoma was selected and two 0.6 mm cores were removed and transferred into a recipient microarray block as described previously 9 . There was no attempt to select areas based on the presence of inflammation or any particular growth pattern.…”

Identification of prognostically relevant and reproducible subsets of endometrial adenocarcinoma based on clustering analysis of immunostaining data

“…For example, in a comparison of ER staining between six laboratories, where the same cases were stained and interpreted according to each laboratories existing protocols, we found there to be excellent interlaboratory agreement (k ¼ 0.84). 54 In the current study we attempted to recapitulate clinical practice by having the slides stained in an independent laboratory, and interpreted by a different team of pathologists. These pathologists used the same guidelines for interpretation described in Material and methods, without a training session (ie their scoring was based on the application of written cutoffs, independent of the first set of pathologists, and without a teaching session to reduce interobserver variation in interpretation).…”

Software Tools for High-Throughput Analysis and Archiving of Immunohistochemistry Staining Data Obtained with Tissue Microarrays

“…11 In a test of interlaboratory variability in estrogen receptor staining, we were able to rapidly identify both highly concordant staining and interpretation for four of five participating laboratories, as well as a significant trend to weaker staining and resulting discrepant results from one laboratory. 12 TMA experiments are a logical follow-up to gene expression microarray experiments that show expression of groups of genes of prognostic or diagnostic significance, and we have undertaken such experiments in follow-up to our earlier gene expression studies of lymphoma, 6 breast carcinoma, 7 and sarcoma. 13 This may be the most fruitful avenue of study as it allows rapid testing of novel potentially diagnostically relevant immunohistochemical markers identified by genome-wide gene expression studies.…”