The epithelial cystic linings and adjacent connective tissues of 61 cases of odontogenic cysts (radicular cysts[RC], dentigerous cysts[DC] and odontogenic keratocysts[OKC]) and unicystic ameloblastomas(UA) were described and compared histopathologically. The type of epithelium in relation to the presence of rete processes and the distribution of chronic inflammatory cells were analyzed statistically. Significant associations between the presence of rete processes in the non-keratinized epithelial linings and inflammation in the subjacent connective tissues of RC and DC were found in this study. There was also a statistically significant association between the presence of rete Processes and nonkeratinized epithelial linings in OKC. The results also showed that in inflamed OKC, the cystic lining epithelium exhibited hyperplasia indistinguishable from lining epithelium of RC and DC. This study further showed that ameloblastomatous-like epithelial cystic linings were present in inflammed odontogenic cysts. All except for one case of unicystic ameloblastomas in this study showed ameloblastomatous epithelial cystic linings. It is recommended that the lining epithelium of RC and DC be examined carefully in order to rule out OKC. Similarly, ameloblastomatous-like lining epithelium arising from chronic inflammation in RC and DC should be differentiated from true ameloblastomatous cystic lining. Such careful examinations are diagnostically important in view of the similarities of epithelial cystic linings of inflamed OKC with DC and RC aggressive behavior ofOKC and UA.
Proliferating Cell Nuclear Antigen (PCNA) is one of the several markers of cellular proliferation. Epithelial proliferations play a significant role in the behaviour of odontogenic lesions. The objective of this study was to describe and compare the distribution of PCNA expression within the epithelial linings of odontogenic cysts. A total of 49 cases of odontogenic cysts consisting of 18 radicular cysts, 16 dentigerous cysts, 15 odontogenic keratocysts (OKCs) was studied. All tissues were processed routinely prior to embedding in paraffin. PCNA immunohistochemical staining was performed on 4 !-tm thick deparaffinized sections mounted on sialinized slides using the peroxidase antiperoxidase method. The distributions of PCNA expression in the cysts linings were noted and comparison was made qualitatively and quantitatively. PCNA labelling index was used for the quantitative assessment. The results showed that PCNA staining was distributed in the basal and supra basal cells for radicular cysts, dentigerous cysts, and OKCs. PCNA labelling index was highest in OKC (22.33±4.07). The high PCNA labelling index in OKC is indicative of high proliferative activity thus supporting previous reports of OKC as the most aggressive type of odontogenic cysts.