Immunohistochemical demonstration of oestrogen and progesterone receptors: correlation of standards achieved on in house tumours with that achieved on external quality assessment material in over 150 laboratories from 26 countries

Abstract

The significant positive correlation between the results obtained on the UK NEQAS tumours and the in house tumours provides evidence for the view that results achieved on EQA material are accurate indicators of in house laboratory performance. Although most laboratories adequately detected tumours with high receptor expression, a large proportion of in house tumours classified initially by participants' staining as being of low or medium ER expression had a higher degree of expression when stained by the UK NEQAS-ICC centre. The efficiency of the organising centre's routine IHC method for ER and PR in optimally demonstrating participants in house breast tumours shows that variations in fixation and tissue preparation are not limiting factors preventing a different laboratory achieving optimal demonstration.