Orthokeratinizing Odontogenic Cyst: A Classification Conundrum

Orthokeratinizing Odontogenic Cyst: A Classification Conundrum

Historically all keratinizing odontogenic cysts have been classified as odontogenic keratocysts. It is becoming apparent that this concept is incorrect and maybe leading to over-aggressive treatment. Distinguishing between Orthokeratinizing Odontogenic Cyst (OOC) and the parakeratinizing version, Keratocystic Odontogenic Tumor (KCOT) is especially prudent when determining if the patient needs to be assessed for Gorlin Syndrome. Currently, the diagnostic criteria for separating these cysts are ill-defined.

Objectives: The aim of this study was to utilize cytokeratin-10 (CK10) as an additional marker to differentiate between OOC and KCOT. We also attempted to establish a more concise histological diagnosis for the two lesions.

Methods: 10 cases of OOC, KCOT, and Dentigerous Cyst (DC) were retrieved randomly from the files of the Oral Pathologic Services at UNMC, College of Dentistry. DC were included as a control as per previous literature review. Formalin-fixed specimens were processed by routine histological methods. Sections were cut at four-microns from paraffin blocks for immunohistochemical staining for monoclonal mouse anti-human CK10 (Dako, Clone DE-K10 ) antigen. Immunohistochemical staining followed an indirect procedure. These slides were then observed and categorized based on cell level staining as well as intensity. H&E sections were also observed and basic histological characteristics were recorded.

Results: Early results show negative CK10 staining in DC which is consistent with current literature. OOC and KCOT both lack CK10 expression in the basal cell layer, but the expression of CK10 varied in intensity and cellular layer in the upper epithelium.

Conclusion: It appears that CK10 staining could be a diagnostic marker in differentiating between OOC, KCOT, and DC. This would allow clinicians to appropriately treat patients with KCOT and refer patients for genetic testing when Gorlin Syndrome is suspected.

This study was funded by the UNMC College of Dentistry Summer Research Fellowship 2007.