✍ Scribed by ÖFNER, DIETMAR; SCHMID, KURT WERNER
No coin nor oath required. For personal study only.
We recently read with great interest the Editorial by Dr Crocker concerning the 'trials and tribulations' of interphase argyrophilic nucleolar organizer region associated proteins ( AgNORs).' We have had experience with this method since 19902 and one of our major aims was to apply AgNOR quantitation reliably and reproducibly in routine histopathology. Thus, we feel encouraged to raise some further important points which were not mentioned in Dr Crocker's Editorial, although these issues were particularly emphasized in the work of our group, to which reference was made.' I t is now generally accepted that conflicting and controversial results achieved in the past were mainly due to the poor quality of AgNOR staining. We have recently shown that AgNQR staining on routinely processed archival tissues can be substantially improved by wet autoclave pretreatment4 of sections prior to the common silver staining.5 On applying this method, the quality of staining was found to be comparable to that obtained on freshly alcohol-fixed material, with AgNORs visible as distinct substructures of the nucleolus. This staining quality can be obtained hoinogeneously throughout the whole section and is apparently independent of tissue origin as well as of duration of formalin fixation and archival storage.h
Secondly, the introduction of morphometric AgNQR analysis and the use of the so-called 'coefficient of variation (CV)" as a parameter reflecting the AgNOR content per nucleus have yielded comparable and reproducible results both between difierent laboratories equipped with different image analysis systems (interobserver variability) and in respect of measurements by the same investigator (intra-observer ~ariability).',~ These two improvements offer the possibility of reliable standardization. They have been proposed by the 'Committee on AgNOR Quantitation' as the present 'gold standard' in AgNQR analysis.' Our recently published study in this journal on adenocarcinomas of the colorectum' was the first paper presenting AgNOR data obtained after standardized staining and computer-aided image analysis. In the meantime, similar studies have been performed on breast"' and lung carcinomas,' confirming the usefulness of the improved AgN OR quantitation.
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