Nucleolar organiser regions in pathology

The value of the AgNOR staining method in identifying carcinoma in situ testis

An early and reliable diagnosis is necessary in order to have the chance of a curative therapy of Carcinoma in situ testis (Cis). Forty-six testicular biopsies were investigated to assess the value of the AgNOR staining method in comparison to placental alkaline phosphatase (PLAP) immunostaining. Both methods provided corresponding results and identical tumor cells were recognized in serial sections. The mean AgNOR counts per nucleus were 26.86 (19-52, SD: 2.68) for CIS cells, 8.18 (5-14, SD: 2.20) for spermatogonia and 12.96 (9-18, SD: 2.44) for Sertoli cells, without the counts overlapping within these three groups. Even single CIS cells are easily and reliably recognizable by their typical AgNOR pattern and their high AgNOR count per nucleus. The independent estimation of 9 testicular biopsies with the AgNOR staining method and the PLAP immunostaining correspondingly revealed 7 biopsies with CIS. Two biopsies lacked tumor cells. The AgNOR staining method can be recommended as an additional diagnostic tool in identifying CIS, because of the short and convenient staining procedure, low costs and the applicability on formalin-fixed and paraffin-embedded material.

Proliferative activity as a prognostic factor in Borrmann type 4 gastric carcinoma

Proliferative activities in 181 primary Borrmann type 4 gastric carcinomas were investigated using percentage labelling of proliferating cell nuclear antigen (PCNA) and an argyrophilic nucleolar organiser region (AgNOR) count. Tumours with a high proliferative activity often metastasised to lymph nodes (P < 0.01), and these patients had a lower survival rate (P < 0.05). A significant correlation was recognised between the PCNA labelling percentage and AgNOR count (r = 0.452, P < 0.001). Cox's regression analysis showed that PCNA labelling percentage is an independent prognostic factor. These results indicate that estimating proliferative activity may be useful in predicting lymph node metastasis and patients' prognosis in cases of Borrmann type 4 gastric carcinoma.

In vitro investigations of interphase and metaphase argyrophilic nucleolar organizer regions and cellular proliferation in the human urothelial cancer cell line HOK-1

Detailed investigation of cell growth and nucleolar organizer region associated argyrophilic proteins (Ag-NORs) is necessary to assess a possible impact of Ag-NOR quantification on the diagnosis and prognosis of tumours. In this study, cellular proliferation of the transitional-cell carcinoma cell line HOK-1 was modulated over a period of 11 days by starvation and subsequent medium addition. Proliferation was determined daily by DNA flow cytometric estimation of S-phase fraction (SPF) and mitotic index (MI) calculation. The number and area of interphase Ag-NORs were quantified by automated image analysis daily and the number of Ag-NOR bearing chromosomes in metaphase was counted. In interphase nuclei, Ag-NOR area showed a highly significant correlation with SPF (p < 0.0001) whereas interphase Ag-NOR number showed significant correlation with MI (p < 0.05). A positive relationship between the number of Ag-NOR bearing chromosomes in metaphases and cellular proliferation was also observed. There is variability in Ag-NOR quantity during interphase and metaphase depending on growth conditions in vitro. Correlations of the number of interphase Ag-NORs with the MI on one hand and Ag-NOR area with SPF on the other provide further evidence that distribution and quantity of Ag-NORs are strongly influenced by the cell cycle phase within the structural-functional unit of the nucleolus.

Image analysis of Ag-NOR proteins in transitional cell bladder cancer

Nuclear organizer regions (Ag-NORs) were visualized using the standard silver-staining technique in biopsy specimens from 112 bladder carcinomas. The area of individual Ag-NOR dots and the area of Ag-NOR protein/nucleus were measured using a Quantimet 570 image analyser and the results were then correlated with clinical, histological, and quantitative prognostic factors, and survival. The mean area of Ag-NOR dots was not significantly related to any of the features analysed. The mean area of Ag-NOR protein/nucleus was related to WHO grade (P = 0.0004), papillary status (P = 0.004), DNA ploidy (P = 0.02), S-phase fraction (P = 0.02), mitotic frequency/mm2 of enoplastic epithelium (P = 0.005), mean nuclear area (P = 0.001), and SD of nuclear area (P = 0.001). In the entire cohort, the mean area of Ag-NOR protein/nucleus was related to progression with a borderline significance (P = 0.09), while in survival analysis only Ag-NOR count/nucleus had prognostic value (P = 0.010). In Ta-T1 tumours, Ag-NOR protein area/nucleus predicted progression (T-category) (P = 0.016) and survival (P = 0.014) significantly. Also, the mean area of individual Ag-NOR dots (P = 0.026) and Ag-NOR count/nucleus (P = 0.014) were related to prognosis in Ta-T1 tumours.

The nucleolus

Nucleoli are the sites of biosynthesis of the ribosomal precursors. They contain may copies of the genes for the main rRNAs (18S- and 28 S-rRNA) in the form of tandemly arranged repeats at the chromosomal nucleolar organizer regions (NORs). They also contain the small rRNA (5S-rRNA) that is synthesized outside the nucleolus, specific nucleolar proteins, among them the factors and enzymes necessary for transcription and transcript processing, and the precursor units of the ribosomes. In man as in may vertebrate species, three main components of nucleoli, besides chromatin, can be detected: fibrillar centres (FC), dense fibrillar component (DCF), and granular component (GC). Within a nucleolus the FCs are in many cases situated in its central region. The DFc forms a network of strands surrounding the FCs, but may sometimes reach for out towards the periphery of the nucleolus. The GC is usually situated in the peripheral regions of the nucleolus. In cells with a low level of ribosomal biosynthesis the nucleoli are small, usually with a single FC and little surrounding DFC and GC ("ring-shaped nucleolus"). In active cells the DFC forms a large network enclosing several, sometimes up to hundreds of FCs, and the GC covers a large area in the periphery ("compact nucleoli"). In cells at the onset of a new stimulation, the DFC is very prominent whereas the FCs are few and small, and the GC is also not very extensive ("reticulate nucleoli"). In some special cell types that are very active other arrangements of the structural components are found. In Sertoli cells, for instance, only one nucleolus is found, or occasionally two, each with a single large FC and a distinct area of GC, both areas being engulfed by DFC intermingled with some peripheral GC. Immunocytological and in situ hybridization studies to localize the rRNA genes within the nucleolus have so far led to divergent results. Both fibrillar components, the FCs and the DFC, have been claimed as the most probable candidates. Transcription of rDNA and the subsequent early steps of ribosome biosynthesis are localized in the DFC, whereas later steps (mature rRNA, preribosomes) are localized in the GC. The FCs may also serve as sites for the preparation of the rDNA for transcription, and as a store for certain nucleolar proteins. During mitosis, parts of the nucleolar proteins remain at the NORs. A direct contact between the nucleolus and the nuclear envelope is frequently observed but is not dependent on nucleolar activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Nucleolar organizer regions are independently associated with a shortened survival in patients with non-small cell lung cancer

We examined nucleolar organizer regions (Ag-NOR) in 102 patients with non-small cell lung cancer (NSCLC). Ag-NOR counts were generally higher in tumours from more advanced stages, or in poorly differentiated adenocarcinomas. Six potential-prognostic indicators included sex, age, year of operation, histology, stage and Ag-NOR count. Stage and Ag-NOR counts had a significant prognostic value in the univariate analysis for 79 patients who died of their lung cancer. In the multivariate analysis, high Ag-NOR counts as well as disease stage were independently associated with a poor prognosis. Furthermore we divided patients into three groups according to their Ag-NOR counts and found that in patients with stage I and II disease higher Ag-NOR counts were associated with shortened survival. This trend did not continue in patients with stage III and IV disease.

Nucleolar organizer regions in myofibroblasts in breast cancer. Relation to cancer cell morphometry, flow cytometry, sex steroid receptor content, tumour histology and prognosis

The number of silver-stained nucleolar organizer regions (Ag-NORs) was counted in stromal myofibroblasts in 125 cases of breast cancer. The mean (S.E.) of Ag-NORs in stromal myofibroblasts was 4.4 (0.1). The number of Ag-NORs in myofibroblasts was related to histological grade (p = 0.028), histological type (p = 0.013), tumour necrosis (p = 0.026), mitotic frequency (p = 0.091) and S-phase fraction (p = 0.032). The number of Ag-NORs in stromal myofibroblasts predicted survival with a borderline significance (x2 = 3.4, p = 0.052) and also in axillary lymph node negative tumours (X2 = 2.8, p = 0.095). The recurrence-free survival in the entire cohort (X2 = 7.1, p = 0.0075) and in axillary lymph node negative tumours (X2 = 7.1, p = 0.0078) could be predicted on the basis of the number of Ag-NORs in stromal myofibroblasts. In axillary lymph node positive tumours the number of Ag-NORs in stromal myofibroblasts had no prognostic value. In multivariate analysis the number of Ag-NORs in stromal myofibroblasts had no independent prognostic value. The results suggest a close interaction between stromal myofibroblasts and epithelial cancer cells in breast cancer, and stromal changes are clearly a subject for further analyses.

Proliferating cell nuclear antigen (PCNA) expression as a prognostic indicator for renal cell carcinoma: comparison with tumour grade, mitotic index, and silver-staining nucleolar organizer region numbers

Proliferating cell nuclear antigen (PCNA) expression in renal cell carcinoma (RCC) was determined by immunohistochemical staining using the PC10 clone. PCNA indices ranged from 2.4 to 53.1 per cent with mean indices of 12.6, 19.0, and 31.6 per cent for grades 1 to 3 RCC and 31.9 per cent for sarcomatoid RCC. There was a significant difference between the indices of grades 1 and 3 and grades 2 and 3 tumours and between grades 1 and 2 RCC and sarcomatoid RCC. AgNOR scores and mitotic indices were determined for each tumour and comparison of PCNA indices with mean AgNOR scores and mitotic indices showed only a weak correlation (PCNA/AgNOR r = 0.406, PCNA/mitotic index r = 0.315). Tumours were divided according to PCNA index (< or = 18 per cent and > 18 per cent) and there was a significant difference in survival between the two groups, for all cases, and for each of the Robson stages. Multivariate analysis using Cox's proportional hazard model showed PCNA index, tumour stage, and mean AgNOR score to be independent predictors of survival, while tumour grade and mitotic index were found to be dependent variables.

Argyrophilic nucleolar organizer regions (AgNORs) in inflammatory pre-malignant and malignant lesions of the uterine cervix

Nuclear organizer regions (NORs) code for ribosomal RNA and are associated with non-histone nucleoproteins, which can be identified by silver staining (AgNORs). AgNORs have been correlated to proliferative activity of tumors and hence may be prognosis-related. The present study evaluates AgNOR counts in inflammatory lesions of the uterine cervix, cervical intra-epithelial neoplasia, and invasive cervical squamous carcinoma. Significant variation in AgNOR counts were observed between the three study groups, with invasive carcinoma showing maximum counts. Further, a highly significant positive correlation was observed between AgNOR counts and tumor progression. These results therefore suggest that AgNOR counts may be of significance in the evaluation of cervical carcinogenesis and could elaborate histopathological diagnosis of cervical lesions.

Thymic epithelial tumours: evaluation of malignant grade by quantification of proliferating cell nuclear antigen and nucleolar organizer regions

Cellular proliferation was studied by quantification of proliferating cell nuclear antigen (PCNA) and argyrophilic nucleolar organizer regions (AgNORs) of cells in 29 thymic epithelial tumours: 8 noninvasive (7 cortical and 1 mixed) thymomas, 11 invasive/metastatic (all cortical) thymomas, and 10 thymic carcinomas. Thymic carcinoma showed the highest percentage of cells positive for PCNA (14.73 +/- 5.419%) and the largest mean number of AgNORs per nucleus (4.89 +/- 0.756). The mean percentage of PCNA-positive cells and number of AgNORs in thymoma groups were as follows: in noninvasive thymoma 2.96 +/- 1.256% and 2.73 +/- 0.647, respectively, and in invasive/metastatic thymoma 4.41 +/- 1.823% and 3.68 +/- 1.148, respectively. The differences in PCNA and AgNORs were statistically significant between thymic carcinoma and each of thymoma groups. The overlap of the values between these tumours was minimal in the PCNA stains, although it was considerable in AgNOR counts as previously noted. However, there was no statistically significant difference in these markers between noninvasive and invasive/metastatic thymomas. These results indicate that thymoma in general is a slow-growing tumour compared with thymic carcinoma and that noninvasive thymoma is similar to invasive/metastatic thymoma with regard to proliferative activity; these latter two tumours may represent an essentially identical type in different stages of progression.

The nucleolar organizer regions in hyperplastic and tumorous lesions of the human liver

The alterations of the argyrophil nucleolar organizer regions (AgNORs) have been studied in hyperplastic and neoplastic human liver lesions. The material studied included: 11 focal nodular hyperplasias (FNH), 3 adenomas, 19 hepatocellular carcinomas (HCC), 2 hepatoblastomas, 8 liver metastases. In 5 cases tumor-free (normal) liver was also available for study. The mean AgNOR numbers were significantly increased in all of these lesions (in FNHs 3.36 +/- 1.43, in the adenomas 2.48 +/- 1.29, in the HCCs 3.32 +/- 1.43, in the hepatoblastomas 3.33 +/- 1.33 and in the metastases 4.86 +/- 1.54) compared to those observed in normal liver (0.86 +/- 0.85). The highly increased AgNOR number in FNHs was particularly surprising and it seemed to us that based on AgNOR numbers the FNHs could be divided into two groups. With the exception of hepatoblastomas in all primary liver lesions the AgNOR counts distributed on a rather broad scale resulting in overlapping in hyperplastic and tumourous cases. The authors concluded that the AgNOR counts reflect only the proliferative activity of a given cell population and at least in the liver they cannot serve as basis for distinction between the hyperplastic, benign and malignant neoplastic lesions.

Nucleolar organizer regions related to morphometry, flow cytometry, sex steroid receptor content, tumour histology and prognosis in female breast cancer

Nuclear organizer regions (Ag-NORs) were visualized and enumerated in biopsy specimens from 158 breast carcinomas and the results were correlated with clinical, histological, quantitative prognostic factors and survival. The number of Ag-NORs was related significantly to histological type (p = 0.003), tubule formation (p = 0.013), histological grade (p < 0.001), mean nuclear area (p < 0.001), SD of nuclear area (p < 0.001), DNA ploidy (p < 0.001), S phase fraction (p = 0.001), mitotic index (p < 0.001), estrogen receptor content (p < 0.001) and progesterone receptor content (p < 0.001). Ag-NORs were independent of tumour size and axillary lymph node status. Neither in the entire cohort (p = 0.16) nor in axillary lymph node negative tumours (p = 0.11) was the number of Ag-NORs related to survival although a clear trend was observed between lowered survival probability and high Ag-NOR count. In multivariate analysis Ag-NORs had no independent prognostic value. The results confirm previous results in that Ag-NORs have no practical prognostic value over already established prognostic factors in breast cancer.

AgNOR counts have no prognostic value in breast cancer

The prognostic significance of silver-stained nucleolar organizer regions (AgNORs) was retrospectively studied among 230 patients with operable invasive breast cancer from a defined urban population. The number of AgNORs was evaluated from routinely processed paraffin sections by light microscopy at a total magnification of x630. The number of AgNORs had no predictive value on the 8-year survival rate corrected for intercurrent deaths (P = 0.2). A high number of AgNORs (> 2.7, the median value) was not related to any other prognostic variable studied except a low S-phase fraction measured by flow cytometry. AgNOR counting does not appear to be a useful prognostic variable in breast cancer.

Nucleolar organiser region (NOR) distribution as a diagnostic marker in oral keratosis, dysplasia and squamous cell carcinoma

Nucleolar organiser regions (NORs) were quantified from a range of oral mucosal biopsies (n = 40) consisting of benign, reactive, dysplastic and carcinomatous lesions, using silver (Ag) staining, to see if AgNOR counts were helpful in distinguishing them. Mean counts were greater in carcinomas (8.37 +/- 6.11) compared to epithelial dysplasias (5.61 +/- 4.63) or benign keratoses (4.51 +/- 2.57). Although these differences were significant, counts in each diagnostic group overlapped so much that they were of no practical value in distinguishing between individual lesions. However, the higher counts found in many carcinomas were due to dispersion of AgNORs within the nucleoplasm, so that the AgNOR type is helpful in making such a distinction. Whether those dysplastic lesions with higher and more dispersed counts represent those at greater risk of malignant transformation awaits longitudinal study.

Prognostic value of nucleolar organizer regions in neuroendocrine tumours of the lung

The value of the number and size of the nucleolar organizer regions (NORs) as prognostic indicators in human neuroendocrine lung tumours was evaluated in a quantitative study of 57 cases, including 33 small cell carcinomas (SCLCs), 9 well-differentiated neuroendocrine carcinomas (WDNECs) and 15 "classic" carcinoids. NORs were visualized on paraffin sections by an argyrophilic technique (AgNOR) and measured by automatic image analysis. In each case, the mean number and area of AgNORs were evaluated; the results were compared with clinical follow-up and survival. AgNOR values for both number and area were significantly higher in SCLCs than in WDNECs and carcinoids. WDNECs had insignificantly higher AgNOR values than carcinoids. Among SCLCs, AgNOR values of the oat cell subtype and the intermediate cell subtype did not differ significantly. Regardless of the histological tumour type, AgNOR values strongly correlated with prognosis, with more and larger AgNORs indicating a more progressive clinical course. In the present study we demonstrate for the first time that the biological behaviour of neuroendocrine lung tumours is correlated with the number and size of AgNORs. Thus the measurement of AgNORs may serve as an additional prognostic indicator in these neoplasms, particularly in the separation of SCLCs from WDNECs with a more favourable prognosis.