Aim:To evaluate and compare immunohistochemical expression of minichromosome maintenance protein-2 (MCM-2) for proliferative activity in the epithelial lining of radicular cyst (RC), dentigerous cyst (DC) and odontogenic keratocyst (OKC) Materials and methods: This retrospective study was conducted on 45 formalin-fixed paraffin-embedded tissue blocks of odontogenic cysts, which were retrieved from the archives. Sections from RC, DC, and OKC were subjected to MCM-2 nuclear staining technique. For each of the specimens, intensity and extent of MCM-2 expressions were evaluated by a comprehensive scoring formula; 100 nuclei were assessed in the epithelial lining of each specimen, under 400× magnification. Scoring was done for positively stained nuclei and expressed as percentage.
Results:The mean (%) MCM-2 immunopositive nuclei in the epithelial lining were higher in OKC cases (10.93%) as compared with RC (10.40%) and DC (3.07%), and the difference was statistically significant between the OKC and DC (p = 0.046). The mean (%) MCM-2 expression in different histopathological grades of inflammation in RC showed a statistically significant difference of MCM-2 expression (%) between cases of mild (n = 4) and severe (n = 2) degrees of inflammation (p = 0.012) and also between cases of moderate (n = 9) and severe (2) degrees of inflammation (p = 0.008). The mean (%) MCM-2 expression in inflamed (n = 8) and noninflamed (n = 4) cases of OKC showed a statistically significant difference. The mean (%) MCM-2 expression in cases of DC with (n = 7) and without (n = 7) inflammation also showed a statistically significant difference (p = 0.033).
Conclusion:The mean (%) MCM-2 expression was higher in OKC cases as compared with RC and DC, which shows that the epithelium of OKC has a higher proliferative capacity than RC and DC. In present samples, the MCM-2 expression in epithelial lining increased, with increasing grades of inflammation, thus supporting the carcinogenic role of inflammation.