Several recent studies have detected genetic and cytogenetic alterations in epithelial odontogenic tumors. However, the detailed mechanisms of oncogenesis, cytodifferention, and tumor progression remain unknown. p63 as p53 homolog gene has been identified at loci 3q27-29. The p53 signaling cascade has an important role in oncogenesis or cyto- differentiation of odontogenic epithelium. Recently, several syndromes associated with p63 gene mutations have shown to include various tooth abnormalities of both the primary and permanent dentition. But little is known about p63 expression in odontogenic tumors, especially ameloblastomas. The purpose of this study were to examine various expression of p63 in ameloblastomas by immunohistochemistry and to clarify the possible biological role of p63 in ameloblastomas. 15 specimens including 6 follicular, 4 plexiform, 3 acanthomatous, and 2 granular cell types were fixed in 10% neutral formalin. 4um thick sections were used for routine H&E and immunohistochemical examinations. After immuno- histochemical satining, they were examined at a final magnification of 400X. For each case a minimum of 1000 nuclei located in the central and peripheral layers were counted in up to 10 consecutive microscopic fields per case. The immunoreactive cells were evaluated semiquantitatively. Immunoreactivity for p63 in all the types of ameloblastomas was higher in peripheral neoplastic cells than in central neoplastic cells. Keratinizing cells in acanthomatous ameloblastoma and granular cells in granular cell ameloblastoma showed markedly decreased reactivity for p63 in acanthomatous and granular cell ameloblastoma. Labelling index of acanthomatous, plexiform, and granular cell type was 86±11%, 81±17% and 83±15% in peripheral area while 88±14%, 82±11% and 76±10% in central area, respectively. Labelling index of follicular type was 17±4% in peripheral area while 21±3% in central area. There was no significant relationship between plexiform, acanthomaous, and granular cell type, while significant relationships between follicular and acanthomatous type, between plexiform and follicular type, and between granular cell and follicular type, respectively. It suggested that p63 expression could paly an important role in the pathogenesis of ameloblastomas. Morever plexiform, acanthomatous, and granular cell type would show more aggressive proliferative potentiality than follicular type.

Ⅰ. Introduction
 Ⅱ. Materials and Methods
 Ⅲ. Results
 Ⅳ. Discussion
 Ⅴ. References

• 박철범(Dental College, Dankook University Oral Histology, Dental College, Dankook University Oral Aging Research Center) | Cheol Beom Park
• 박경주(Dental College, Dankook University Department of Oral Pathology, Dental College, Dankook University Oral Aging Research Center) | Gyeong Ju Park
• 이종헌(Dental College, Dankook University Oral Histology, Dental College, Dankook University Oral Aging Research Center) | Chong Heon Le correspondence