Quantitative and qualitative analysis of argyrophilic nuclear organizer regions in follicular cyst, keratocystic odontogenic tumor and ameloblastoma

Background: Multicystic ameloblastoma is a benign odontogenic tumor that exhibits a more aggressive behavior than keratocystic odontogenic tumor (KCOT) and follicular cyst.
Aim: The purpose of the study was to evaluate the proliferation index nuclear organizer regions (NORs) and their distribution among the four odontogenic lesions with known different clinical invasive behavior.
Study and Design: In a descriptive-analytical cross-sectional study, 60 paraffin blocks of odontogenic lesions were prepared for silver nitrate staining.
Materials and Methods: For the quantitative analysis, 100 cells were counted at ×100 and the mean value was calculated. The morphometric analysis of NORs showed that they can be distributed into normal (round to oval-shaped) and abnormal (large, bean-shaped and cluster-shaped) groups. One-way analysis of variance (ANOVA) and multiple comparison with Tukey test were used for the statistical analysis of the results.
Results: The argyrophilic NOR (AgNOR) numbers in multicystic ameloblastoma, unicystic ameloblastoma, KCOT, and follicular cyst were 7.4 ± 2.7, 6.1 ± 2.56, 4.7 ± 1.84, and 2.82 ± 1.052, respectively. The difference between ameloblastoma (unicystic and multicystic types) and either_KCOT, or follicular cyst was statistically significant (P<0.001) and, (P=0.001), respectively. In follicular cysts, normal AgNOR dots were not detected outside the nuclei. NOR histological patterns of KCOT were large, bean shaped and rarely cluster shaped and it was cluster-shaped in multicystic and unicystic ameloblastoma.
Conclusion: The current study suggests that determination of clinical behavior of ameloblastoma in comparison with KCOT and follicular cyst in silver nitrate staining is related to higher proliferation activity and different NORs′ distribution pattern. However, further clinical follow-up studies must be performed to prove this.

Keywords
Ameloblastoma, argyrophilic nuclear organizer region, follicular cyst, keratocystic odontogenic tumor