Reliability of human epidermal growth factor receptor 2 immunohistochemistry in breast core needle biopsies.
OBJECTIVE
Core needle biopsies (CNBs) are widely used to determine human epidermal growth factor receptor 2 (HER2) status in breast cancer. Recent publications reported up to 20% false-positive results on CNBs if immunohistochemistry (IHC) is compared with fluorescent in situ hybridization (FISH). To clarify, if confirmation of IHC positivity by FISH is generally required, we analyzed the reliability of IHC positivity on CNBs versus surgical specimens in a multi-institutional study.


METHODS
Five pathologic laboratories contributed to this study by performing IHC on 500 CNBs and the corresponding surgical specimens overall. If IHC revealed score 2+ or 3+, HER2 status was confirmed by FISH in a central laboratory. We compared evaluation according to US Food and Drug Administration-approved scoring criteria and recently published American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines.


RESULTS
CNBs scored 3+ revealed five false-positive results if scoring followed the US Food and Drug Administration criteria (five of 40; 12.5%) and two false-positives in terms of the ASCO-CAP criteria (two of 33; 6.1%). IHC was false negative in one CNB only. By contrast, IHC on surgical specimens revealed five false-negative results, but only one false-positive result (one of 35; 2.9%) if scored following US Food and Drug Administration-approved criteria. With the aid of the ASCO-CAP criteria, false-positive IHC results were obtained in only one of the five participating institutions.


CONCLUSIONS
IHC 3+ scores on CNBs proved to be reliable in four of the five participating institutions if scoring followed the ASCO-CAP criteria. Therefore, accurate determination of HER2 status in breast cancer is possible on CNB using the common strategy to screen all cases by IHC and retest only 2+ scores by FISH. Prerequisites are quality assurance and the application of the new ASCO-CAP criteria.
Lebeau
Annette
A
Department of Pathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. a.lebeau@uke.de
Turzynski
Andreas
A
Braun
Susanne
S
Behrhof
Wera
W
Fleige
Barbara
B
Schmitt
Wolfgang D
WD
Grob
Tobias J
TJ
Burkhardt
Lia
L
Hölzel
Dieter
D
Jackisch
Christian
C
Thomssen
Christoph
C
Müller
Volkmar
V
Untch
Michael
M
D001707:Biopsy, Needle; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015203:Reproducibility of Results
D018719:Erb-b2 Receptor Tyrosine Kinases