The Enigmatic Odontogenic Keratocyst: A Cross-sectional Study of Odontogenic Cysts and Tumors Using Ki-67.

Background: An odontogenic keratocyst is presently considered a cyst by the 2017 World Health Organization (WHO) classification, even though, at times, it shows highly aggressive behavior and a high recurrence rate. Ki-67 is a protein associated with the proliferative activity of the intrinsic cell populations. In tumors, Ki-67 is associated with tumor aggressiveness. This study aimed to compare the Ki-67 expression rates of odontogenic keratocysts to those of other odontogenic cysts and normal mucosa.

Materials and methods: A retrospective cross-sectional study was conducted using pathology samples retrieved from the archives of a tertiary care center to evaluate Ki-67 expression. Histopathologically confirmed cases of odontogenic keratocysts, radicular cysts, dentigerous cysts, and ameloblastomas were selected. The standardized immunohistochemistry streptavidin-biotin detection system HRP-DAB method was employed for analysis.

Results: All the odontogenic keratocysts pathology samples demonstrated some degree of Ki-67 expression: mild, moderate, and severe Ki-67 expressions were identified in 26.7%, 53.3%, and 20.0% of the samples, respectively. Compared to the odontogenic keratocyst samples, the samples from dentigerous cysts, periapical cysts, ameloblastomas, and normal mucosa demonstrated no Ki-67 expression in 33.3%-66.7% of the samples, mild expression in 13.3%-40.0%, moderate expression in 0%-33.3%, and severe expression in none of the samples (P<0.001).

Conclusions: Ki-67 was either moderately or severely overexpressed in the majority of odontogenic keratocyst samples. The 2017 WHO classification, which reclassifies keratocystic odontogenic tumors as cysts, conflicts with our findings.