Suitability of Histology to Predict the Ploidy Status of Tumours

Objectives: DNA aneuploidy, as determined with high-resolution flow cytometry, has been shown to be an independent predictor of survival in oral squamous cell carcinoma (OSCC). High-resolution flow cytometry is based on using DAPI (4'6-di-amidino -2- indolphenol) as the DNA stain. The use of DAPI is unfortunately relatively limited since it requires UV excitation, which is not a common light source in most standard flow cytometers. Determination of ploidy status, mainly through image cytometry, is becoming important as a marker to predict the behaviour and possible malignant progression of oral premalignant lesions. Both high-resolution flow cytometers and image cytometers capable of ploidy determination are not commonly available. This study was undertaken to determine the suitability of histological features alone as a predictor of the ploidy status. Methods: H&E sections of 82 cases of primary OSCC were analysed by four experienced Oral Pathologists. They were asked to predict the ploidy status of all the tumours using histological features. Fresh material was available in all the cases of OSCC for ploidy determination using high-resolution flow cytometry. Results: The percentage of cases of which the ploidy status was correctly predicted by the four Oral Pathologists varied between 51% to 66%. A better predictive value was obtained regarding the aneuploid tumours (50% - 84%). Conclusions: This study has shown that histological features are not a reliable marker to accurately determine the ploidy status of OSCC.