Evaluation of AgNOR count in distinguishing benign from malignant mesothelial cells in pleural fluids

A Case-Control Study of Oral Epithelial Proliferative Markers among Sudanese Toombak Dippers Using Micronuclei Assay, Argyrophilic Nucleolar Organizer Region, Papanicolaou and Crystal Violet Methods

The use of Toombak has been reported to play a major role in the etiology of oral cancer in Sudan. The cellular proliferative activity on the oral epithelium of 210 Toombak dippers was assessed by applying the micronuclei frequency, mean argyrophilic nucleolar organizer region (AgNOR) counts, Papanicolaou method, and 1% crystal violet stain. Participants were divided into 3 groups: 200 were apparently healthy individuals, 100 were Toombak users (cases), 100 were non-tobacco users (control) and 10 were patients with oral squamous cell carcinomas. Cytological atypia was identified among 4 (4%). Toombak users and was not found among the control group (P<0.04). The micronuclei frequencies were higher in Toombak users (1.026) than in the control group (0.356) (P<0.0001). The mean AgNOR counts in Toombak users (2.423) were higher than control group (1.303) (P<0.0001). Neither Toombak users nor control group showed mitotic figures in 1% crystal violet method. The results of this research showed that Toombak dipping is a high risk factor for increase in the cellular proliferation in the oral mucosa. The cytological proliferative marker methods used are useful for screening Toombak users.

The use of epithelial membrane antigen and silver-stained nucleolar organizer regions testing in the differential diagnosis of mesothelioma from benign reactive mesothelioses

BACKGROUND

The accurate diagnosis of pleural lesions obtained from small closed biopsy is difficult. As yet there is no single reliable test to distinguish between malignant and benign mesothelial tissue.

METHODS

Immunostaining of epithelial membrane antigen (EMA) and the quantitation of silver stained nucleolar organizer regions (AgNORs) each were applied to benign and malignant histologic sections of pleural and peritoneal biopsies. The usefulness of these stains was tested both individually and in combination in the diagnosis of epithelial malignant mesothelioma.

RESULTS

One hundred and three of the 141 malignant lesions (73%) were immunoreactive for EMA but only 3 of the 73 benign lesions (4%) reacted equivocally, and none positively. The average count of AgNORs/cell in malignant lesions (n = 80) was elevated compared with benign cases (n = 26), but a significant overlap was exhibited in the AgNOR count and this form of analysis was considered to be of little value in distinguishing benign from malignant mesothelial processes. Much less overlap was observed when the average AgNOR area was measured. By using the maximum benign AgNOR area of 0.6677 microm2 as the upper threshold, 51 cases (63.8%) were identified as malignant; the test demonstrated 100% specificity and 63.8% sensitivity. By combining the EMA and AgNOR results, 76 of 80 of the malignant mesothelioma cases (95%) tested positive for at least 1 of the tests with no false-positive results identified.

CONCLUSIONS

This study confirms the usefulness of EMA in diagnosing malignant and benign mesothelial lesions, and demonstrates the enhanced diagnostic value of combining EMA immunoreaction with the average area of AgNOR per cell, thereby increasing sensitivity in the diagnosis of epithelial malignant mesothelioma.

Comparison of silver-staining nucleolar organizer region (AgNOR) counts and proliferating cell nuclear antigen (PCNA) expression in reactive mesothelial hyperplasia and malignant mesothelioma

Previous workers have used counts of colloidal silver-stained nucleolar organizer regions (AgNORs) to help distinguish reactive from malignant mesothelial processes. We sought to compare the demanding technique of AgNOR counting with the identification of proliferating cell nuclear antigen (PCNA) in 10 pleural malignant mesotheliomas and 11 reactive mesothelial proliferations. The mean AgNOR count was significantly higher in malignant compared to reactive lesions (5.10 [95% confidence interval, CI 4.35-5.84] vs 3.68 [95% CI 3.17-4.19], p = 0.004), as was the PCNA index (26.9 [95% CI 17.37-36.49] vs 9.67 [95% CI 4.94-14.39], p = 0.004). Less overlap was seen with PCNA indices and no reactive mesothelial proliferations had a PCNA index greater than 20%, suggesting that scores over this level may be a specific indicator of malignancy in this setting. There was only a weak correlation between the 2 proliferation indices suggesting that PCNA and AgNORs are present at somewhat different times of the cell cycle and/or persist in the post-S phase cell for variable lengths of time.