Standardized staining and analysis of argyrophilic nucleolar organizer region associated proteins (AgNORs) in radically resected colorectal adenocarcinoma—correlation with tumour stage and long-term survival

Quantification of silver-stained nucleolar organizer region associated proteins (AgNORs) was introduced in histopathology as a marker of cellular and nucleolar activity. However, due to the poor staining quality obtained on routinely processed archival material, the method yielded controversial and sometimes non-reproducible results. The recent introduction of wet autoclave pretreatment has reliably improved AgNOR staining quality on routinely formalin-fixed and paraffin-embedded tissues. In the present study, 92 routinely processed colorectal carcinomas were investigated, applying this novel staining technique. Subsequent standardized morphometric analysis revealed, irrespective of common tumour staging or grading classifications, a statistically highly significant correlation between AgNOR parameters and clinical course. The usefulness of standardized AgNOR parameters for the independent prediction of patient survival was proven by uni- and multivariate analysis.