Nucleolar organiser regions (AgNORS) in anal intraepithelial neoplasia and invasive anal squamous cell carcinoma.

AIM To evaluate the usefulness of counting nucleolar organiser region associated proteins (AgNORs) in the management of anal squamous neoplasia. METHOD Using a silver staining technique for NOR associated proteins, 32 routinely processed paraffin wax embedded sections of anal epithelium were assessed. These consisted of normal anal epithelium (n = 9), anal intraepithelial neoplasia (AIN) grades I (n = 5), and III (n = 13), and invasive squamous neoplasia of the anus (n = 5). RESULTS The median AgNOR counts for every 100 cells are as follows: normal anal epithelium 2.15 (95% CI 1.89-3.94); AIN I 3.21 (95% CI 2.89-7.14); AIN III 4.32 (95% CI 4.00-8.10); and invasive squamous cell carcinoma of the anus 5.51 (95% CI 2.48-10.62). There were significant differences between AgNOR counts in anal cancer and normal epithelium (p < 0.05; Mann-Whitney U test)), AIN III and normal anal epithelium (p < 0.005), and AIN III and AIN I (p < 0.05). No significant differences were observed between AIN I and normal anal epithelium, anal cancer and AIN I, and anal cancer and AIN III. There was a considerable degree of overlap among the different groups. CONCLUSIONS Despite the strong association between AgNOR values and degree of dysplasia, the variability within pathological grade may preclude the adoption of this technique on its own as a prognostic indicator. It may, however, be useful in conjunction with other markers of neoplastic growth such as c-myc oncogene amplification or overexpression as a marker of disease progression in AIN and invasive anal squamous cell cancer.