Immunohistochemical Study of the Orthokeratinized Odontogenic Cyst: a Comparison with the Odontogenic Keratocyst

Objective: Orthokeratinized odontogenic cyst (OOC) is a developmental cyst that occurs in the maxilla and the mandible and is defined by the World Health Organization as the uncommon orthokeratinized type of odontogenic keratocyst (OKC). However, studies have shown that OOC has peculiar clinicopathologic aspects and biologic behavior when compared with other developmental odontogenic cysts, especially OKCs. Therefore, in this study, the immunohistochemical profile of the OOC was delineated and compared with that of the OKC.

Study Design: Twelve cases of OOC were submitted to a panel of antibodies composed of cytokeratins (10, 13, and 14) and extracellular matrix proteins: fibronectin, types I and III collagen, and tenascin. For comparative means, 12 cases of OKC also were submitted to the same panel of antibodies.

Results: The results obtained showed that OOCs expressed cytokeratin 10 and showed variable expression of cytokeratins 13 and 14. Fibronectin and collagen types I and III also were expressed in OOC in a fibrillar aspect. OKC showed only the superficial keratin layer positive to cytokeratin 10 and the basal and suprabasal layers with variable expression of cytokeratin 14, and cytokeratin 13 was present in the upper epithelial layers. The extracellular matrix proteins showed a nonfibrillar expression. Tenascin was immunoexpressed only in OKC.

Conclusion: The immunohistochemical profile of the studied cysts clearly showed that OOC presents a well-formed cystic enveloping, whereas the OKC profile is compatible with a more aggressive biologic behavior.