11
Figure 5. Clinical Question 4 "Group 3"
HER2/CEP17 ratio<2.0
Average HER2 signals/cell ≥6.0
Assess IHC using sections from the
same tissue sample used for ISH
IHC 0/1+
HER2/CEP17
ratio <2.0
Average HER2
signals/cell ≥6.0
IHC 3+
HER2 Negative
with Comment
a
a
Comment: ere are insufficient data on the efficacy of HER2-targeted therapy in cases with HER2
ratio <2.0 in the absence of protein over-expression because such patients were not eligible for the
first generation of adjuvant trastuzumab clinical trials. When concurrent IHC results are negative
(0–1+), it is recommended that the specimen be considered HER2 negative.
Other ISH Result
Observer blinded to previous
results recounts ISH,
counting at least 20 cells
Result should be
adjudicated per
internal procedures
to determine final
category
IHC 2+
HER2 Positive
HER2 Positive
