Investigating the Role of DNA Ploidy and Proliferation Index in Distinguishing Ameloblastoma from Ameloblastic Carcinoma

Abstract Purpose This study aimed to investigate the role of DNA ploidy and proliferation index in distinguishing ameloblastoma (AB) from ameloblastic carcinoma (AC). Methods The study included 29 ACs, 6 conventional ABs that transformed into ACs, and a control cohort of 20 conventional ABs. The demographics and clinicopathologic details of the included cases were summarised and compared. The Ki-67 proliferation index was scored using the QuPath open-source software platform. DNA ploidy analysis was performed using high-resolution flow cytometry. Results The cohort of ABs presented at an overall younger age compared to both primary and secondary ACs. There was a statistically significant difference between the median duration of the tumour when comparing primary and secondary ACs, with ACs presenting with longer durations than the AB cohort. All cases of AC showed a relatively high median proliferation index of 41.7%, with statistically significant higher scores compared to ABs. DNA ploidy analysis showed that all cases in the AB cohort were diploid. Two diploid cases of AB that transformed into ACs were aneuploid when the corresponding secondary AC was analysed. Fourteen cases of AC were diploid and 12 were aneuploid, with no statistically significant association found between DNA ploidy status of primary and secondary ACs. A statistically significant difference was noted when the DNA ploidy status of ABs was compared to that of ACs. When comparing the Ki-67 proliferation score of ACs to their DNA ploidy status, no statistically significant association was noted. Conclusion DNA ploidy analysis and proliferation index via Ki-67 IHC are useful ancillary tests that may be used to support a diagnosis of AC and may assist in distinguishing between challenging cases of AB and AC.