Absence of BRAFV600E immunohistochemical expression in sporadic odontogenic keratocyst, syndromic odontogenic keratocyst and orthokeratinized odontogenic cyst

Background: Odontogenic keratocyst (OKC) is a unique developmental odontogenic cyst that has the potential to behave aggressively and is associated with the nevoid basal cell carcinoma syndrome. Orthokeratinized odontogenic cyst (OOC) is a distinct, uncommon odontogenic cyst. It significantly differs from OKC not only in its epithelial lining but also in proliferating kinetics, clinical, immunohistochemical and biological behaviour. BRAF gene located on chromosome 7q34 encodes a cytoplasmic serine-threonine kinase. Various immunohistochemical studies have been conducted to express the BRAFV600E gene mutation in various odontogenic cyst and tumours with varying results. The present study was conducted to evaluate the possible role of BRAFV600E in the pathogenesis of sporadic OKC, syndromic OKC and OOC by immunohistochemistry.

Methods: Formalin-fixed paraffin-embedded (FFPE) tissue blocks of 15 diagnosed cases each of sporadic OKC, syndromic OKC and OOC were retrieved from the archives of Department of Oral Pathology and subjected to immunohistochemical staining for the detection of BRAFV600E mutation using a novel rabbit monoclonal antibody clone RM8.

Results: Immunohistochemical analysis showed complete absence of BRAFV600E mutation in all cases of sporadic OKC, syndromic OKC and OOC.

Conclusion: The negative immunohistochemical expression of BRAFV600E in sporadic OKC, syndromic OKC and OOC suggests that BRAFV600E plays no role in the pathogenesis of sporadic OKC, syndromic OKC and OOC.