Table 4.

23 cases with locally equivocal IHC for determination of HER2 positivity (shaded cells indicate discordance between central laboratories)

	Mayo central
	HER2 negative			HER2 positive
IEO central	IHC neg / FISH neg	IHC equ / FISH neg	IHC equ / FISH equ	IHC equ / FISH pos	IHC pos / FISH pos	Total
HER2 negative
IHC neg / FISH neg	3	3	--	1	--	7
IHC equ / FISH neg	--	1	--	1	--	2
IHC equ / FISH equ	--	--	--	2	1	3
HER2 positive
IHC equ / FISH pos	--	1	--	1	3	5
IHC pos / FISH pos	--	--	--	--	6	6
Total	3	5	0	5	10	23

IHC immunohistochemical, HER2 human epidermal growth factor receptor 2, FISH fluorescent in situ hydridization, Mayo Mayo Clinic central laboratory, IEO European Institute of Oncology central laboratory, neg negative, equ equivocal, pos positive