QUALITATIVE ENHANCEMENT OF THE DNA PLOIDY ANALYSIS CRITERIA TO ASSESS MALIGNANT TRANSFORMATION RISK

Background DNA ploidy analysis is arguably the most sensitive and reproducible approach to assess risk in oral potentially malignant disorders. Although aneuploidy has been associated with a high risk of malignant transformation (MT), the current diagnostic criteria of aneuploidy are not specific to oral mucosal tissues and thus yield positive predictive values (PPVs) ranging from 30% to 40%. Objective The aims of this study were to analyze the ploidy status of archived material diagnosed as oral leukoplakia (OL) with follow-up data on MT and to review the risk classification criteria. Methods Nuclei suspensions were enzymatically prepared from formalin-fixed, paraffin-embedded tissue from 121 patients with OL and stained with propidium iodide for flow cytometry. Twenty-three patients had MT. Histograms were initially analyzed for the proportion of nuclei in G1 phase (2c), S phase, G2 phase (4c), and 5c-exceeding rate (5cER). Histograms diagnosed as aneuploid were further investigated qualitatively on the basis of nuclei distribution pattern. Log-rank test on Kaplan-Meier curves (LRKM; P Results Seven aneuploid histogram types were detected, of which only 3 proved truly high risk. EAR was then stratified as low risk (diploid), medium risk (low-risk aneuploid), and high risk, whereas TAR remained as diploid (low risk) and aneuploid (high risk). Aneuploidy in TAR had PPV of 55%, SS of 88%, and SP of 81% (LRKM P Conclusions Enhancement of TAR based on qualitative histogram classification significantly improves predictive values. Flow cytometry is an accessible approach to assess MT risk in OL.