. 2022 Jul 5;1(1):7. doi: 10.1007/s44178-022-00007-8

Table 6.

Interpretation of ISH test results

HER2/CEP17 ratio	Average HER2 copy number	ISH status interpretation
< 2.0	< 4.0	Negative
	≥ 4.0 and < 6.0	It is recommended to recount 20 cells, and if the result changes, then comprehensively analyze the two results; if the result remains unchanged and the IHC is 2+, it is deemed negative.
	≥ 6.0	It is recommended to increase the number of counted cells; if the result remains unchanged, it is deemed positive
≥ 2.0	< 4.0	It is recommended to increase the number of counted cells; if the result remains unchanged, it is deemed negative
≥ 2.0	≥ 4.0	Positive

Low HER2 expression means IHC 1+ and/or 2+ and negative ISH.