Immunoexpression of RANK, RANKL and OPG in sporadic odontogenic keratocysts and their potential association with recurrence.

Background: Odontogenic keratocysts (OKCs) are clinically aggressive lesions with relatively high recurrence rates. Dysregulation of functional equilibrium in the RANK/RANKL/OPG system is responsible for osteolysis associated with the development of OKCs. Previously published findings imply that immunoexpression of these 3 proteins may correlate with bone resorption activity in OKCs.
Objectives: The rationale behind this study was to assess the potential for receptor activator of nuclear factor kappa-B (RANK), receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) expression, as well as RANKL/OPG expression ratio, to serve as prognostic indicators for OKC recurrence.
Material and Methods: We investigated the immunoexpression patterns of RANK, RANKL and OPG, and their correlation with recurrence rates, in 41 patients with OKCs treated with enucleation.
Results: We found no statistically significant differences between recurrent and non-recurrent cysts in terms of either: epithelial (p = 0.404) and stromal (p = 0.469) immunoreactivity of RANK; epithelial (p = 0.649) and stromal (p = 0.198) immunoreactivity of RANKL; or epithelial (p = 1) and stromal (p = 0.604) immunoreactivity of OPG. We also did not find significant differences in the distribution of cases with respect to ratios of RANKL/OPG immunostaining scores between recurrent and non-recurrent OKCs, both in the epithelium and in the connective tissue (p = 1 and p = 0.237, respectively).
Conclusions: Our results suggest that immunoexpression levels of RANK, RANKL and OPG at the time of pathological diagnosis, as well as the RANKL/OPG ratio, are not useful as prognostic markers for OKC recurrence.