The Role of DNA Ploidy and Ki-67 in the Grading of Mucoepidermoid Carcinomas

Background: The grading of mucoepidermoid carcinomas (MEC) is based on subjective microscopic evaluation of the prevalence of cell types as well as features of atypia and aggressiveness. Our study was aimed at evaluating the role of high-resolution DNA flow cytometry and Ki-67 expression in the grading of MEC. Materials and Methods: Fifty-five cases of intraoral and major salivary gland tumours, diagnosed as MEC, were retrieved and the grading system proposed by Brandwein et al. applied. Results: Forty-nine per cent of our sample was graded as high, 35% as intermediate and 16% as low. Eighty-nine per cent of the high-grade MEC showed aneuploid DNA cell populations, while 88% of the diploid tumours were graded as intermediate or low. The mean Ki-67 positivity was significantly different between the high and intermediate grade tumours and between the aneuploid and diploid tumours. Conclusion: This study showed that high-resolution DNA flow cytometry of archival paraffin-embedded tissue is accurate in the grading of MEC and can be used with Ki-67 expression as an additional diagnostic tool.