Table 1. Source, dilution and cut-off values for positivity for different biomarkers.

Marker	Antibody (Source)	Optimal dilution	Positive-control tissue	Cut-off values for positivity
ck5/6	D5/16 B4 (Dako UK Ltd, Ely, Cambridgeshire, UK)	1 : 100	Tonsil	10%
ck14	LL002 (Vector Labs, Peterborough, UK)	1 : 100	Skin	10%
ER	1D5 (Dako UK Ltd)	1 : 100	Breast	1%
PGR	PGR 636 (Dako UK Ltd)	Neat	Breast	1%
HER2	DakoA0485 (Dako UK Ltd)	1 : 500	Breast	30% membranous (corresponds to IHC 3+), or if IHC 2+, confirmed by FISH+
p53	DO7 (Dako UK Ltd)	1 : 100	Breast	10% nuclear
EGFR	EGFR.113 (Dako UK Ltd)	1 : 50	Skin	10% membranous
Topo2α	KI-S1 (Dako UK Ltd)	1 : 100	Tonsil	45% nuclear (high)
KI67	MIB1 (Dako UK Ltd)	1 : 100	Tonsil	10% nuclear (high)

Positive-control tissue is also indicated. Positive HER2 was defined as presence of membrane expression of the protein in >30% of tumour cells (corresponds to IHC 3+) or if underexpressed (2+), confirmed by FISH (fluorescent in situ hybridisation). For p53, Topo2α and Ki67, 100 nuclei were scored for positivity in four random fields ( × 40 magnification) and the total percent-score obtained. Median values of Topo2α were chosen as cut-offs for high or low expression. Other standard cut-offs as per Rakha et al (2006, 2007).