Immunohistochemical comparison of cyclin D1 and P16 in odontogenic keratocyst and unicystic ameloblastoma

Background: The different growth mechanism and biologic behavior of the odontogenic keratocyst (OKC) compared to other odontogenic cysts might be related to the proliferating capacity of its epithelium. In this study, the aim was to evaluate and compare the distribution and staining intensity of P16 and cyclin D1 in OKC and unicystic ameloblastoma (UA). Materials and Methods: In this descriptive analytic study, hematoxylin‑ and eosin‑stained slides of OKCs and UAs available from the archives of the oral pathology laboratory of the Esfahan School of Dentistry were examined. Twenty‑five noninflamed solitary odontogenic keratocysts and 25 unicystic ameloblastomas (of either type) were selected and stained immunohistochemically. Distribution and staining intensity score (SID score) for P16‑ and cyclin D1‑positive cells was calculated in both groups. Results were analyzed statistically with Wilcoxon, Friedman, and Mann‑Whitney tests; P < 0.05 was considered significant. Results: The highest expression of Cyclin D1‑positive cells was seen in the suprabasal layer of keratocysts (P < 0.05) and in the peripheral layer of UAs (P < 0.05). Likewise, the highest expression of P16‑positive cells was observed in the basal and suprabasal layers of keratocysts (P > 0.05) and central portions of UAs (P > 0.05). Expression of Cyclin D1 was higher in UAs compared to keratocyts (P < 0.05), although P16 did not show a significant difference between the two study groups (P > 0.05). Conclusion: Cyclin D1 did show a higher staining intensity in UAs compared to the keratocysts, although the expression of P16 was similar in the studied groups. The invasive growth of OKC might be related to the state of expression of cyclin D1 and P16 in the epithelium of this cyst.