Argyrophilic nucleolar organizer regions (AgNORs) in ameloblastomas and adenomatoid odontogenic tumours (AOTs)

Quantitative analysis of Argyrophilic Nucleolar organizer regions in odontogenic cysts and tumor - A comparative study

Background

The nucleolar organizer region (NOR) is by definition part of a chromosome, and nucleolus is a structure containing this chromosomal part and in addition the material which accumulate around the NOR, mostly rRNAs and their precursors as well as specific ribosomal proteins. Argyrophilic Nucleolar organizing region (AgNOR) are silver binding NORs often used to study cell proliferation in various types of tumors.

Aim

Quantitative assessment of Argyrophilic Nucleolar organizing region count and its comparison among dentigerous cyst, keratocystic odontogenic tumor and ameloblastoma.

Material and method

Forty-five histologically confirmed cases, 15 cases each of keratocystic odontogenic tumor, dentigerous cysts and ameloblastomas were examined for Argyrophilic Nucleolar organizing region. The sections were obtained and Argyrophilic Nucleolar organizer regions staining was done for comparing the proliferative capacity among these lesions.

Result

Post hoc analysis for inter-group comparison and one way ANOVA were done in all three groups in this study. P < 0.001 was considered significant. The results of AgNOR counts were higher in KCOTs as compared to ameloblastoma and least in dentigerous cysts. The mean AgNOR counts between the study groups were compared using one way ANOVA test and the differences were found to be significant (P < 0.001).

Conclusion

AgNOR counts were significantly higher in KCOT and ameloblastoma as compared to dentigerous cyst suggesting that these lesions have a higher proliferative capacity than dentigerous cyst. The finding of a significantly higher AgNOR counts in KCOT as compared to ameloblastoma represent a difference in proliferative activity and greater growth potential between these two lesions.

Quantitative assessment of silver-stained nucleolar organizer region in odontogenic cysts to correlate the growth and malignant potentiality

Context:

The most common and important odontogenic cyst involving jaws is the odontogenic keratocyst (OKC) or primordial cyst, the dentigerous cyst and the radicular cyst. These cysts all though do not show similar behavior, they all have the potentiality to recur. Silver nitrate staining of the nucleolar organizer regions (AgNORs) of the benign and malignant lesions is becoming very useful as a diagnostic indicator. Thus, the aim of this study is to assess the diagnostic potential of AgNORs in the cystic epithelium of common odontogenic cysts.

Materials and Methods:

Archived specimens of odontogenic cysts were stained with hematoxylin and eosin stain and AgNOR stain.

Results:

The comparative evaluation of the AgNOR counts was done among the three varieties of odontogenic cysts, i.e., radicular cysts, dentigerous cysts and OKC and were observed that the mean for OKC was significantly higher than that of radicular cyst.

Conclusion:

Therefore, AgNor could be used as an efficient tool for comparative evaluation of microscopic features such as epithelial thickness, surface keratinization and mural proliferation in dentigerous cyst to that of the AgNOR count.

Analysis of silver stained nucleolar organizing regions in odontogenic cysts and tumors

Objective:

The present study aimed to investigate the probable differences in cell proliferation index of odontogenic cysts and tumors by means of a comparative silver stained nucleolar organizing region (AgNOR) quantification.

Study Design:

This descriptive cross-sectional study was done on archival paraffin blocks (n = 62), consisting of 10 odontogenic keratocysts, 10 dentigerous cysts, 10 radicular cysts, 10 conventional ameloblastomas, 10 adenomatoid odontogenic tumors, 10 calcifying epithelial odontogenic tumors and 2 ameloblasic carcinomas.

Results:

The mean AgNOR count of odontogenic cysts was 1.709 and the benign odontogenic tumors was 1.862. Highest AgNOR count was recorded in odontogenic keratocyst and lowest was seen in radicular cyst. Statistically significant difference in AgNOR counts of ameloblastoma and adenomatoid odontogenic tumor, amelobalastoma and calcifying epithelial odontogenic tumor, benign odontogenic tumors and ameloblastic carcinoma were seen. AgNORs in ameloblastic carcinoma were more in number and more widely spread.

Conclusion:

AgNOR technique may be considered a good indicator of cell proliferation in odontogenic cysts and tumors.

Molecular biomarkers of cell proliferation in ameloblastomas

Cell proliferation is a vital biological process that is important for all living organisms because of its role in growth and the maintenance of tissue homeostasis. The control of this important process differs greatly among benign and malignant neoplasms, and the evaluation of cell proliferation in neoplasms has become a common tool used by pathologists to provide useful information pertaining to diagnosis, clinical behavior, and treatment. The usefulness of information regarding cell proliferation has led to numerous studies on the value of these methods for diagnosing different types of tumors and for clinical decision making. Ameloblastomas are no exception. This review discusses the use of several classical molecular proliferation markers, including Ki-67, proliferating cell nuclear antigen, cyclin D1 and DNA topoisomerase II alpha, to characterize ameloblastomas and proposes the use of new proliferation markers used previously to characterize other neoplasms. The use of these biomarkers offers valuable opportunities to evaluate the biological behavior of this type of odontogenic tumor.

c-Myc oncogene expression in selected odontogenic cysts and tumors: An immunohistochemical study

Aim:

To investigate the role of c-Myc oncogene in selected odontogenic cysts and tumors.

Materials and Methods:

Ten cases each of ameloblastoma, adenomatoid odontogenic tumor (AOT), odontogenic keratocyst (OKC), dentigerous cyst, and radicular cyst were selected and primary monoclonal mouse anti-human c-Myc antibody was used in a dilution of 1: 50. Statistical Analysis was performed using Mann Whitney U test.

Results:

80% positivity was observed in ameloblastoma, AOT and OKC; 50% positivity in radicular cyst and 20% positivity in dentigerous cyst. Comparison of c-Myc expression between ameloblastoma and AOT did not reveal significant results. Similarly, no statistical significance was observed when results of OKC were compared with ameloblastoma and AOT. In contrast, significant differences were seen on comparison of dentigerous cyst with ameloblastoma and AOT and radicular cyst with AOT.

Conclusion:

From the above data we conclude that (1) Ameloblastoma and AOT have similar proliferative potential and their biologic behavior cannot possibly be attributed to it. (2) OKC has an intrinsic growth potential which is absent in other cysts and reinforces its classification as keratocystic odontogenic tumor.

Comparative morphometric study of AgNORs in variants of ameloblastoma

Aims:

To compare the area and number of AgNORs (silver stained nucleolar organizer regions) by morphometry between follicular and plexiform variants of ameloblastoma in order to analyze their cell proliferation rates.

Materials and Methods:

This retrospective study was carried out on 30 cases each of follicular and plexiform ameloblastoma. The sections were obtained and stained with silver staining technique to identify the nucleolar organizer regions. AgNORs were quantified using two parameters; manual tag for the number of AgNORs and area measurement using the image analyzer software, Image-Pro-Express.

Results:

Morphometric area measurements of AgNOR were significantly higher for Plexiform ameloblastoma (0.831μm²) than follicular ameloblastoma (0.528μm²). Enumeration of the number of AgNORs showed a significantly higher number of AgNOR for follicular ameloblastoma (1.71) than plexiform ameloblastoma (1.43). Among the groups studied, follicular ameloblastoma was more aggressive than plexiform ameloblastoma, as it showed smaller AgNOR area and higher AgNOR number.

Conclusion:

The combination of counting the number and measuring the area of AgNOR dots showed a significant overall difference between AgNOR profiles of follicular and plexiform variants of ameloblastoma.

Study on the origin and nature of the adenomatoid odontogenic tumor by immunohistochemistry

The adenomatoid odontogenic tumor (AOT) is a clinically benign lesion. Discussions about the AOT hamartomatous or neoplastic nature, and the probable odontogenic epithelial cell it originates from still exist. This research aimed to study and discuss the subject by the immunohistochemical detection of cytokeratins, laminin, collagen IV, PCNA and p53 in 8 tumor samples and 8 dental follicle samples containing reduced enamel epithelium. The results have shown that CK14 labelling indicated differentiation grades for secreting ameloblasts or ameloblasts in the post-secreting stage in the adenomatoid structure of AOT. Laminin, found on the luminal surface of adenomatoid structures, was compatible with the reduced enamel epithelium during the "protective stage of amelogenesis". PCNA specifically labelled the spindled areas and peripheral cords of the AOT, indicating that these areas are responsible for tumor growth. After considerations about pathogenesis, the authors suggested that the nature of AOT is hamartomatous with histogenesis from the reduced enamel epithelium.

Quantitative analysis of argyrophilic nucleolar organizer regions and epidermal growth factor receptor in ameloblastomas

OBJECTIVE

The aim of this study was to evaluate the proliferation activity by means of the quantification of the argyrophilic nucleolar organizer regions (AgNORs) and the patterns of expression of the epidermal growth factor receptor (EGFR) in ameloblastomas.

METHOD

The methods of evaluation included the H/E stain for the morphologic analysis, the silver impregnation technique for quantification of the AgNORs and the immunohistochemical stain with anti-EGFR antibody in 11 cases of ameloblastoma.

RESULTS

The results did not show a significant statistical difference as per quantification of the AgNORs. The expression of the EGFR on the epithelial islands of ameloblastoma was not uniform, and the location of the expression was also variable. The predominant expression was that of cytoplasm and the islands with an expression of membrane only were rare and generally smaller in size.

CONCLUSION

The tumor presents an irregular growth. Smaller islands are associated with a higher proliferation activity and therefore could be responsible for tumor infiltration.

Proliferating cell nuclear antigen (PCNA) and p53 protein expression in ameloblastoma and adenomatoid odontogenic tumor

In this study, proliferating cell nuclear antigen (PCNA) and p53 protein expressions were analyzed in 16 cases of ameloblastoma and 8 cases of adenomatoid odontogenic tumor (AOT). The cases of ameloblastoma consisted of solid type tumors and histologic arrangements of different subtypes were observed. In some specimens, more than one histologic subtype was identified in the same lesion, and each tumor was categorized according to the predominant cell pattern. The odontogenic tumors were grouped as follows: follicular ameloblastoma (n=7), plexiform ameloblastoma (n=4), acanthomatous + follicular ameloblastoma (n=3), basal cell ameloblastoma (n=2), adenomatoid odontogenic tumor (n=8). PCNA immunohistochemical expression revealed stronger quantitative labeling index for the follicular ameloblastoma, while for p53 protein the strongest quantitative labeling index was detected in the plexiform type. Nevertheless, statistical analysis using ANOVA and Tukey's test did not detect significant differences (p>0.05) among the histologic subtypes of ameloblastoma. The findings of this study suggest that the different histologic patterns of ameloblastoma did not show a direct correlation with their clinical behavior and consequently with the prognosis of the cases. The results also indicated that the ameloblastoma has greater proliferative potential than the AOT, which can contribute to explain its more aggressive and invasive characteristics.

Nucleolar organizer regions in selected odontogenic lesions

OBJECTIVE

The present study aimed to assess the usefulness of argyrophilic nucleolar organizer regions (AgNORs) as quantitative criteria in the diagnosis of odontogenic cysts and tumors.

STUDY DESIGN

This descriptive cross-sectional study was done on archival paraffin blocks (n = 37), consisting of 10 conventional ameloblastomas, 7 cases of unicystic ameloblastoma, 10 odontogenic keratocysts, and 10 dentigerous cysts, all accessioned between 1994 and 2000.

RESULTS

The findings showed a significant statistical difference among the 4 lesions (P <.001). Conventional and unicystic ameloblastomas had a significantly higher (P <.05) number of AgNORs than odontogenic keratocysts and dentigerous cysts. No significant differences were observed within each group of tumors or cysts. The number of AgNORs was also significantly higher (P <.005) in the nuclei of basal layer cells of the epithelial lining of keratocysts than in the nuclei of parabasal layer cells. AgNORs in conventional and unicystic ameloblastomas were smaller but more broadly distributed, which may indicate higher proliferative activity.

CONCLUSION

AgNORs can be useful in the histopathologic differentiation of ameloblastomas from odontogenic cysts.

Identification of the AgNORs, PCNA and ck16 proteins in oral lichen planus lesions

The expression of proliferating cell nuclear antigen (PCNA), cytokeratin 16 (ck16) and Ag nucleolar organizer regions (AgNORs) were assessed in 20 cases of lichen planus, 20 cases of keratosis and 20 cases of normal oral mucosa in order to evaluate the rate of keratinocyte proliferation in these tissues. Three hundred cells were counted in each sample: 100 basal cells, 100 suprabasal cells and 100 squamous cells. The mean number of AgNORs and the percentage of PCNA positive cells were calculated. Except from similar staining of suprabasal cells of lichen planus and keratosis, PCNA and AgNORs values were higher in all layers of lichen planus than in both keratosis and normal oral mucosa. The three groups showed similar ck16 immunostaining: all of the cells were positive, except those of the basal layer. The results suggest that the keratinocyte proliferation index is higher in lichen planus than in keratosis and normal mucosa. Besides, ck16 should not be used to differentiate the entities studied.