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.