Clinical importance of HER2 immunohistologic
heterogeneous expression in core-needle
biopsies vs resection specimens for equivocal
(immunohistochemical score 2þ) cases
Mamatha Chivukula1, Rohit Bhargava1, Adam Brufsky2, Urvashi Surti3and David J Dabbs1
1Department of Pathology, Magee Women’s Hospital of UPMC, Pittsburgh, PA, USA;2Department of Medical
Oncology, Breast Cancer Care Center, Magee Women’s Hospital of UPMC, Pittsburgh, PA, USA and
3Department of Cytogenetics Magee, Women’s Hospital of UPMC, Pittsburgh, PA, USA
HER2 oncoprotein is overexpressed in 15–20% of breast carcinomas and is associated with poor outcome. The
2þ group is considered equivocal, since gene amplification is observed in some but not others. The aim of our
study is to ascertain if there is clinical significance to heterogeneity of HER2 immunohistologic expression in
breast core-needle biopsies vs surgical resection specimens. A total of 37 invasive breast carcinomas
diagnosed on core-needle biopsies and scored 2þ by HER2 immunohistochemical assay were selected from
our files. The results were obtained on these selected cases, of which 19 cases were nonamplified and 18 cases
were amplified. The follow-up resection specimens were reviewed and two additional tumor blocks were
selected in each case for HER2 immunostaining. The 74 tissue blocks were examined for HER2 using antibody
clone CB11 on the Benchmark XT and scored as negative (score 0 or 1þ), weakly positive (2þ) or strongly
positive (3þ). Results within the amplified group, 56% (11/18) showed significant areas with 3þ score in both
blocks, 28% (5/18) remained as 2þ, 11% (2/18) showed score 0–1þ. In the nonamplified group, 42% (8/19) had
score 0–1þ, 37% (7/19) remained as 2þ, 0% (0/19) had score 3þ. Five (5) cases showed heterogeneous
staining in both the groups. In the amplified group, 56% of cases showed strong 3þ in both the blocks of which
half of these cases had areas of 2þ. Fluorescence in situ hybridization was performed on a representative
resection specimen block. In the amplified group 72% (13/18) cases were amplified, 22% (4/18) were
nonamplified. In the nonamplified group, no amplification is detected in a great majority of cases 89%
(17/19). HER2 immunohistochemistry on core-needle biopsies is usually predictive of tumor HER2 status.
However, performing fluorescence in situ hybridization on core-needle biopsies almost completely resolves the
issue of heterogeneous expression of HER2.
Modern Pathology (2008) 21, 363–368; doi:10.1038/modpathol.3801021; published online 1 February 2008
Keywords: HER2; FISH; core-needle biopsy; breast carcinoma; IHC; Herceptin
HER2 is a proto-oncogene, located on chromosome
17 and is amplified in 15–20% of breast carcinomas,
which signifies a poor prognosis and predicts a poor
response to hormonal therapy.1,2American Society
of Clinical Oncology and National Comprehensive
Cancer Network guidelines recommend HER2 test-
ing for all primary breast carcinomas.2,3Assessment
of HER2 status of breast carcinomas is critical for the
management of advanced breast cancer. With the
recent focus on the targeted therapies and latest
introduction of Trastuzumab (Herceptins), a huma-
nized monoclonal antibody to the extracellular
domain of HER2, appears to be promising for the
patients with metastatic breast carcinoma. However,
due to the cardiotoxic effect of this drug, it becomes
important to evaluate the HER2 status accurately
and select patients who will benefit from the
HER2 proto-oncogene amplification is usually
accompanied by protein overexpression. The ampli-
fication is generally determined by fluorescent
in-situ hybridization (FISH) method and the protein
expression is determined by immunohistochemis-
try. In a typical pathology laboratory, both assays
are performed on formalin-fixed paraffin-embedded
Received 23 July 2007; revised 5 December 2007; accepted 7
December 2007; published online 1 February 2008
Correspondence: Dr M Chivukula, MD, Department of Pathology,
Magee Women’s Hospital of UPMC, 300 Halket Street, Pittsburgh,
Modern Pathology (2008) 21, 363–368
& 2008 USCAP , Inc All rights reserved 0893-3952/08 $30.00
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Clinical importance of HER2 immunohistologic heterogeneous expression
M Chivukula et al
Modern Pathology (2008) 21, 363–368