Objective: The aim of this study is to evaluated the nuclear DNA content of ameloblastomas and its correlation to the histological type and the different clinical behavior. Methods: 9 ameloblastomas (follicular, plexiform, acanthomatous) and 1 ameloblastic carcinoma were studied by DNA flow cytometry on paraffin-embedded tissue. Four 50 micron sections were cut from tissue blocks, dewaxed in xylene and rehydrated through alcohol solutions. Single cell suspensions were obtained following incubation in 0.5% pepsine-saline solution. After 30 minutes of incubation in pepsine, the cells were washed and stained with propidium iodide and buffer system. DNA content was measured with the FACS can flow cytometer of Becton Dickinson. Results: Seven of ten ameloblastomas showed cells with normal diploid DNA content (DNA-index 1.00). Three cases were uninterpretable. The coefficient of variation (CV) ranged from 5.37% to 7.58% with a mean of 6.24%. Tumor CVs of less than 6% for fresh or frozen material and less than 8% for paraffin-embedded material are recommended. The coefficient of variation is used as a measure of instrument alignment and of the quality of staining. The percentage of S- phase ranged from 5.21% to 15.7%, with a mean of 9.68% and median of 8.86%. Conclusion: No significant correlatin between the histologic type, recurrent ameloblastomas and malignancy and nuclear DNA content (ploidy) was seen; increasing S-phase percent was associated with neoplastic trasformation in one case (ameloblastic carcinoma).

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