2006 Volume 5 Issue 1 Pages 43-49
Keratocystic odontogenic tumor (KCOT), called formerly as odontogenic keratocyst (OKC), is newly classified in the odontogenic tumor by the revised WHO histological classification in 2005, because of its potential for aggressive behavior, high local recurrence rate and the involvement of PTHC gene mutation in etiology. We examined the cytokeratin expression and proliferative activity of KCOT/OKC and compared them to non-keratinized primordial cyst (PC), in order to better understand its nature. The epithelial layers of KCOT/OKC and PC revealed almost the same cytokeratin expression to CK 7, 13, 19, 20 and HMW, but showed the different expression to CK 17 (KCOT/OKC, + ; PC, -). The LIs for Ki-67 and topoisomerase IIα were higher in KCOT/OKC (23.1 ; 10.4) than in the PC (9.8 ; 3.6), and Student's t test demonstrated a significant difference (p<0.01) in both LIs between KCOT/OKC and PC. There was a strong correlation between the Ki-67 LI and the topoisomerase IIα LI (Pearson's correlation coefficient r=0.91), suggesting that their combined use is recommended to estimate the proliferative activity. CK 17 might be related to the proliferative lesions. It is considered that KCOT/OKC behaves biologically as a tumor and belongs a different entity to PC.
