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Endocrine Surgery Unit, Department of Surgical and Gastroenterological Sciences, University of Padua, School of Medicine, via Giustiniani 2, 35128 Padova, Italy
1 Biostatistics Unit, Department of Neurosciences, University of Padua, School of Medicine, via Giustiniani 2, 35128 Padova, Italy
2 Department of Pathology, University of Padua, School of Medicine, via Giustiniani 2, 35128 Padova, Italy
(Requests for offprints should be addressed to F Lumachi; Email: flumachi{at}unipd.it)
| Abstract |
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| Introduction |
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The aim of this study was to evaluate the usefulness of DNA flow cytometry to determine tumour nuclear DNA index (DI), and nucleolar organizer region (NOR) protein counts visualized by the argyrophil (AgNOR) technique, in confirming diagnosis and predicting clinical outcome of patients with PC.
| Materials and methods |
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All patients died of the disease, 21146 months (median 29 months) after the first operation.
NOR silver staining and AgNOR measurement
Sections of 3 µm, cut from blocks routinely processed in paraffin wax, were dewaxed in xylene and ethanol, post-fixed for 30 min in 3:1 absolute ethanolacetic acid solution and rehydrated (Ploton et al. 1986, Trerè et al. 1991). AgNOR staining was performed with a solution obtained by dissolving gelatine in aqueous formic acid (.nal concentration 2 g/dl) mixed with a 50 g/dl aqueous silver nitrate solution (Ploton et al. 1986). Silver staining was done at room temperature. The numbers of AgNOR, visualized as distinct black dots, were counted by means of an image-analysis system, using a graphic monitor (Crocker & Nar 1987). AgNOR counting was performed on 100 randomly selected nuclei of parathyroid cells, using a x100 oil-immersion objective lens (Kanematsu et al. 1997). The mean number of AgNORs per nucleus in each specimen was recorded in a database.
Nuclear DNA content
Sections of 30 µm were deparaffinized as described above. As suggested by Obara et al.(1990), disaggregation was obtained by using 0.5% pepsin solution at pH 1.5. The sample was filtered (40 µm nylon mesh), and the single-cell nucleus suspension was resuspended in a solution containing propidium iodine and ribonuclease A. Flow cytometer measurement was used, and 20 000 nuclei were read for each sample (Obara et al. 1990, Bosci et al. 1998). The DNA content was interpreted as diploid if only one G0/ G1 peak was present (DI = 1.0), and the DI was calculated as the ratio of the peak channel number of the aneuploid G0/G1 peak to the peak channel number of the diploid G0/G1 peak (August et al. 1993).
Statistical analysis
Differences between means (that is, biochemical parameters) were tested by unpaired Students t-test, while the Fisher exact test was used for fractions. The Spearman rho calculation was used to evaluate the linear relationship between age, biochemical parameters and size of the tumour and survival. The logistic regression model was used to identify factors independently predicting the clinical outcome. In the multivariate analysis, only the variables found to be significant in the univariate analysis were used.
Median survival time (MST) was calculated by the KaplanMeier method, while differences in MST were tested for statistical significance by the log-rank test. The differences were considered significant at a P value of <0.01.
| Results |
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The survivals of patients with aneuploid (n = 11) and diploid (n = 4) PC were 74.0 ± 58.1 and 34.1 ± 18.4 months (P = 0.21) respectively. No correlation was found between survival and the main preoperative clinical and biochemical parameters (Table 4
). There was a significant relationship between DI and AgNOR counts (rho = 0.69, P < 0.01), but no correlation (P = NS) was found between survival and both AgNOR counts and DI (Fig. 2
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| Discussion |
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Neither tumour size nor lymph node status appear to predict survival in patients with PC, but the reported 5- and 10-year survival rates are approximately 85% and 50% (Shane 2001). The classic pathological features are not always present in all patients with PC, although 70% of patients may exhibit local invasion (Clayman et al. 2004). Moreover, recurrence is common, and persistent or recurrent disease may be observed at 120 years (Kebebew et al. 2001). Patients with PC should have lifelong follow-up, and different parameters should be considered to predict the biological behaviour of the tumour. Bondeson et al.(1993) showed a positive correlation between morphological variables such as fibrosis, necrosis, nuclear atypia and mitotic figures, and an aberrant DNA pattern demonstrated by image cytometry. August et al.(1993), reviewing nine patients with PC, found that four of the five patients with evidence of tumour aneuploidy died of metastatic disease, while the four patients with diploid tumours were disease free at 18 years after the first operation. They concluded that DNA cytometry may help differentiate patients whose PC is likely to be indolent (diploid tumours) from those with a tumour (aneuploid) more likely to be aggressive. Unfortunately, the aneuploid DNA pattern occurs in too large a fraction of benign parathyroid lesions to be useful for differentiating between PA and PC (Mallette 1992, Obara et al. 1997). However, the DNA ploidy pattern may be a valuable prognostic factor to predict recurrence (Obara et al. 1990, 1997). We found aneuploid tumours in 11 of 15 patients with PC, and in three of 15 patients with PA. Overall, DI (mean±S.D.) was significantly (P < 0.01) higher in patients with PC than those with PA, but no correlation (P = NS) was found between DI and survival.
It is difficult to determine the prognosis for patients with PC solely from the results of tumour DNA cytometry, and some studies considered the DI to be of no value in deciding the benign or malignant character of a parathyroid tumour (Obara et al. 1990, Kameyama et al. 1999). Thus, parameters other than DI were investigated, such as proliferating cell nuclear antigen (PCNA), the cell cycle-associated antigen Ki-67 and AgNOR counts. Few studies consider the usefulness of labelling indices of PCNA and Ki-67 positivity as markers of the biological behaviour of PC (Abbona et al. 1995, Kameyama et al. 2000). Kanematsu et al.(1997), studying 25 parathyroid lesions of which three were PC, found that the AgNOR numbers were significantly higher in PC than in PA. The authors concluded that AgNOR may be useful as an adjunct in discriminating PC from benign parathyroid disease. More recently, the multivariate analysis of Tuccari et al.(2000) showed that the mean area of AgNORs per cell (NORA) was unrelated to age, sex, main biochemical parameters and tumour size in a group of 10 patients with PC. A significantly higher mean NORA value was observed in patients with distant metastasis than in those with no clinical evidence of disease progression. However, surprisingly, only one patient died of disease at a mean follow-up of more than 80 months. We have not found any correlation (P = NS) between survival and AgNOR counts in our patients.
We conclude that DI and AgNOR are useful in confirming diagnosis of PC; however, they are of little value in predicting the clinical outcome of patients with PC.
| Acknowledgements |
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