COMPARISON OF PROLIFERATING CELL NUCLEAR ANTIGEN EXPRESSION IN ODONTOGENIC KERATOCYST AND AMELOBLASTOMA - AN IMMUNOHISTOCHEMICAL STUDY

Proliferating cell nuclear antigen (PCNA) is a nuclear protein synthes ized in the late G1 and S phase of the cell cycle, and immunohistochem ical detection of the protein represents a useful marker for the proli ferating fraction of cells in tissue specimens. PCNA expression was st udied in odontogenic keratocysts (n = 15) and ameloblastomas in = 46) using an avidin-biotin-peroxidase complex method on routinely processe d paraffin sections. The percentage of PCNA-positive cells determined by point counting was significantly lower in the ameloblastomas (mean 9.4% standard deviation (SD) 11.0) than in odontogenic keratocysts (me an 29.9%, SD 24.0). In ameloblastomas, the mean percentage of PCNA-pos itive cells was lowest in the acanthomatous pattern and highest in ple xiform pattern. The mean percentage of PCNA-positive cells in plexifor m pattern was non-significantly higher than that in follicular pattern . The mean percentage of PCNA-positive cells in plexiform and follicul ar patterns was significantly higher than that in cyctic and acanthoma tous patterns. The frequency of PCNA-positive cells was significantly higher in the peripheral cells of follicular, and, plexiform patterns than in the central cells of both patterns ip < 0.01). Therefore, peri pheral cells were regarded as reserve cell of central cells. The mean percentage of PCNA-positive cells in the epithelial lining of odontoge nic keratocyst was not significantly different from those in the perip heral cells of follicular and plexiform patterns of ameloblastoma. In contrast, the odontogenic keratocyst exhibited a mean percentage of PC NA-positive cells which was statistically higher than that in other hi stological elements of ameloblastomas, The present study suggests that odontogenic keratocyst is regarded as benign odontogenic tumour.