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HER2 overexpression of breast cancers in Hong Kong: prevalence and concordance between immunohistochemistry and in-situ hybridisation assays
TK Yau,
H Sze,
IS Soong,
F Hioe,
US Khoo,
AWM Lee
Department of Clinical Oncology, Pamela Youde Nethersole Eastern
Hospital, Chai Wan, Hong Kong
OBJECTIVES. To evaluate the prevalence of human epidermal growth factor
receptor 2 (HER2) gene overexpression in breast cancer patients
encountered in Hong Kong and the concordance of HER2 findings
from primary immunohistochemistry assays and confirmatory
in-situ hybridisation assays.
DESIGN. Retrospective study.
SETTING. Department of Clinical Oncology in a public hospital in Hong
Kong.
PATIENTS. All patient referrals between July 2006 and June 2007 with newly
diagnosed invasive breast cancer (for prevalence evaluation),
and all patients treated at our unit with confirmatory in-situ
hybridisation tests performed within the study period (for
concordance evaluation).
RESULTS. There were 272 consecutive breast cancer patients eligible
for prevalence evaluation. The distribution for immunohistochemistry
staining in 249 cases for scores 0, 1+, 2+, and 3+ were
99 (40%), 40 (16%), 58 (23%), and 52 (21%) respectively. In the
remaining 23 patients, four and 19 breast cancers were unscored
and reported by immunohistochemistry to be HER2-positive
and -negative, respectively. The overall HER2 overexpression
rate (3+ or reported as positive) was 21%. HER2 overexpression
was associated with grade 3 histology (P<0.001) and negative
hormonal receptor status (P<0.001). However, it was not
associated with age (P=0.525), T-classification (P=0.740), N-classification
(P=0.691), nor group stages (P=0.433). Of the 37
patients with confirmatory in-situ hybridisation tests performed,
10 (71%) of 14 with immunohistochemistry staining of 3+ and
1 (4%) of 23 with immunohistochemistry staining of 2+ were
found to have HER2 gene amplification.
CONCLUSIONS. More than 25% of HER2 overexpression identified by
immunohistochemistry assays in this Hong Kong cohort could
not be verified by confirmatory in-situ hybridisation assays.
Compliance with the latest guidelines for HER2 testing should
improve the future accuracy and concordance.
Hong Kong Med J 2008;14:130-5
Key words: Breast neoplasms; Gene amplification;
Immunohistochemistry; In situ
hybridization, fluorescence; Receptor,
epidermal growth factor
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