Dysregulation of the cell cycle is an important factor in a potentially malignant oral disorder. There have not been many studies on the role of the cell cycle regulator p27 in oral non-homogenous leukoplakia. The aim of our study was to characterise the p27 protein in homogenous and non-homogenous oral leukoplakias (OL), in comparison with healthy mucosa and squamous cell carcinoma tissues. The current study included 25 patients with OL, 15 cases with oral squamous cell carcinoma, and 15

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... s of healthy oral mucosa, both as comparison groups. Immunohistochemical p27 antigen expression was determined by a standard EnView imaging system. The expression level of p27 in nodular and verrucous leukoplakia was lower than in homogenous OL but higher than in erythroleukoplakia. There was a statistically significant difference (p < 0.05) between the expression of p27 in healthy mucosa and homogenous OL. There was a significantly lower amount of p27 positive cells in oral cancer than in OL (p < 0.0001); however, its intracytoplasmic presence was diagnosed. Our study proved the instability of p27 protein and its dual nature in non-homogenous OL and OSCC, and therefore, it can be used as a predictive marker for the clinical course of these conditions.